diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5fd9156..20b19cc 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -6,8 +6,14 @@ set(CMAKE_CXX_STANDARD 14)
 include_directories(.)
 
 add_executable(stackoverflow_in_cpp
-    AbstractUser.h
-    Exceptions.h
-    main.cpp
-    User.cpp
-    User.h)
+        AbstractUser.h
+        Exceptions.h
+        Content.h
+        Content.cpp
+        ContentRelation.h
+        ContentRelation.cpp
+        Logger.cpp
+        Logger.h
+        main.cpp
+        User.cpp
+        User.h)
diff --git a/Content.cpp b/Content.cpp
new file mode 100644
index 0000000..d12ae40
--- /dev/null
+++ b/Content.cpp
@@ -0,0 +1,28 @@
+#include "Content.h"
+
+Content::Content(std::string &body, ContentType type): visits(0), type(type), body(body) {}
+
+Content::~Content() {
+    for(int i = 0; i < relations.size(); i++)
+        delete relations[0];
+}
+
+void Content::add_relation(ContentRelationType type, Content &destination) {
+    auto relation_ptr = new ContentRelation(&destination, this,  type);
+    relations.push_back(relation_ptr);
+    destination.relations.push_back(relation_ptr);
+}
+
+void Content::edit_content(std::string &body) {
+    this->body = body;
+}
+
+void Content::print_answers() {
+    int answer_number = 1;
+    for(int i = 0; i < relations.size(); i++) {
+        if(relations[i]->type == ANSWER_TO) {
+            std::cout << answer_number++ << ". " << relations[i]->source->body << std::endl;
+        }
+    }
+    std::cout << std::endl;
+}
diff --git a/Content.h b/Content.h
new file mode 100644
index 0000000..0681543
--- /dev/null
+++ b/Content.h
@@ -0,0 +1,25 @@
+#pragma once
+
+#include <iostream>
+#include <vector>
+#include "ContentRelation.h"
+
+enum ContentType {
+    QUESTION,
+    ANSWER
+};
+
+class Content {
+public:
+    std::string body;
+    ContentType type;
+    int visits;
+    std::vector<ContentRelation*> relations;
+
+public:
+    Content(std::string &body, ContentType type);
+    ~Content();
+    void add_relation(ContentRelationType type, Content &destination);
+    void edit_content(std::string &body);
+    void print_answers();
+};
diff --git a/ContentRelation.cpp b/ContentRelation.cpp
new file mode 100644
index 0000000..60ab2fc
--- /dev/null
+++ b/ContentRelation.cpp
@@ -0,0 +1,25 @@
+#include "ContentRelation.h"
+#include "Content.h"
+
+ContentRelation::ContentRelation(Content *destination, Content *source, ContentRelationType type):
+    destination(destination),
+    source(source),
+    type(type) {}
+
+ContentRelation::~ContentRelation() {
+    auto relations = &(this->destination->relations);
+
+    for(auto it = relations->begin(); it < relations->end(); it++) {
+        if(*it == this) {
+            relations->erase(it);
+        }
+    }
+
+    relations = &(this->source->relations);
+
+    for (auto it = relations->begin(); it < relations->end(); it++) {
+        if (*it == this) {
+            relations->erase(it);
+        }
+    }
+}
diff --git a/ContentRelation.h b/ContentRelation.h
new file mode 100644
index 0000000..c0f1cb2
--- /dev/null
+++ b/ContentRelation.h
@@ -0,0 +1,22 @@
+#pragma once
+
+#include <iostream>
+#include<vector>
+
+enum ContentRelationType {
+    DUPLICATE_OF,
+    ANSWER_TO
+};
+
+class Content;
+
+class ContentRelation {
+public:
+    ContentRelation(Content* destination, Content* source, ContentRelationType type);
+    ~ContentRelation();
+
+public:
+    Content* destination;
+    Content* source ;
+    ContentRelationType type;
+};
diff --git a/Exceptions.h b/Exceptions.h
index f304c0b..8bce64f 100644
--- a/Exceptions.h
+++ b/Exceptions.h
@@ -11,7 +11,6 @@ class UsernameAlreadyExistsException : public std::exception {
 
 private:
     const std::string message = "Error: username already exists";
-
 };
 
 class EmailAlreadyExistsException : public std::exception {
@@ -22,16 +21,38 @@ class EmailAlreadyExistsException : public std::exception {
 
 private:
     const std::string message = "Error: email already exists";
+};
 
+class InvalidUsernameException : public std::exception {
+public:
+    const char *what() const throw() {
+        return message.c_str();
+    }
+
+private:
+    const std::string message = "Error: invalid username\n"
+                                "You can use a-z, 0-9 and underscores\n"
+                                "Username must be at least 5 and at most 32 characters";
 };
 
-class WrongUsernameOrPasswordException : public std::exception {
+class InvalidEmailException : public std::exception {
+public:
+    const char *what() const throw() {
+        return message.c_str();
+    }
+
 private:
-    const std::string message = "Error: wrong username or password!";
+    const std::string message = "Error: invalid email address";
+};
+
+class WrongUsernameOrPasswordException : public std::exception {
 public:
     const char *what() const throw() {
         return message.c_str();
     }
+
+private:
+    const std::string message = "Error: wrong username or password!";
 };
 
 class DeleteAdminException : public std::exception {
@@ -42,5 +63,4 @@ class DeleteAdminException : public std::exception {
 
 private:
     const std::string message = "Error: can't delete admin account!";
-
 };
diff --git a/Logger.cpp b/Logger.cpp
new file mode 100644
index 0000000..c23e90c
--- /dev/null
+++ b/Logger.cpp
@@ -0,0 +1,45 @@
+#include "Logger.h"
+#include "User.h"
+#include <iostream>
+#include <fstream>
+#include <vector>
+#include <ctime>
+
+Logger::Logger() {
+    std::ifstream file;
+    int num = 1;
+    while(true) {
+        file.open("log." + to_string(num) + ".txt");
+        if(file.is_open()) {
+            file.close();
+            num++;
+            continue;
+        }
+        log_num = num;
+        std::ofstream log_file("log." + std::to_string(log_num) + ".txt");
+        break;
+    }
+}
+
+Logger& Logger::getInstance() {
+    static Logger lg;
+    return lg;
+}
+
+void Logger::log(User& user) {
+    std::ofstream log_file("log." + std::to_string(Logger::getInstance().log_num) + ".txt", std::ios::app);
+    time_t now = time(0);
+    std::string date_time(ctime(&now));
+    log_file << user << " | " << date_time;
+    this->logs.push_back(user.toString() + " | " + date_time);
+}
+
+void Logger::printLogs() {
+    for(auto &log : logs) {
+        std::cout << log << std::endl;
+    }
+}
+
+std::vector<std::string>& Logger::getLogs() {
+    return this->logs;
+}
diff --git a/Logger.h b/Logger.h
new file mode 100644
index 0000000..1e0f446
--- /dev/null
+++ b/Logger.h
@@ -0,0 +1,22 @@
+#pragma once
+
+#include <vector>
+#include <string>
+#include "User.h"
+
+#define _Log(x) Logger::getInstance().log((x))
+
+
+class Logger {
+public:
+    static Logger& getInstance();
+public:
+    void printLogs();
+    void log(User& user);
+    std::vector<std::string>& getLogs ();
+private:
+    Logger();
+    std::vector<std::string> logs;
+private:
+    int log_num;
+};
diff --git a/User.cpp b/User.cpp
index 7aa9f46..88d12a0 100644
--- a/User.cpp
+++ b/User.cpp
@@ -1,14 +1,20 @@
 #include <utility>
 
-//
-// Created by spsina on 11/8/18.
-//
-
 #include <sstream>
 #include "User.h"
 #include "Exceptions.h"
 #include <iostream>
+#include <regex>
+
+bool is_username_valid(const string& username) {
+    const std::regex pattern("\\w{5,32}");
+    return std::regex_match(username, pattern);
+}
 
+bool is_email_valid(const string& email) {
+    const std::regex pattern("(\\w+)(\\.|_)?(\\w*)@(\\w+)(\\.(\\w+))+");
+    return std::regex_match(email, pattern);
+}
 
 vector<User> User::users;
 string User::salt;
@@ -71,7 +77,15 @@ User& User::signup(string username, string password, string email){
             throw EmailAlreadyExistsException();
         }
     }
-    //Create user
+    // Check username validatin
+    if(not is_username_valid(username))
+        throw InvalidUsernameException();
+
+    // Check email validatin
+    if(not is_email_valid(email))
+        throw InvalidEmailException();
+
+    // Create user
     users.emplace_back(username, password, email, UserType::MEMBER);
     return users[users.size() - 1];
 }
@@ -80,4 +94,55 @@ void User::init(const string &salt) {
     User::salt = salt;
     users.reserve(20);
     users.emplace_back("admin", "admin", "admin@stackoverflow.com", UserType::ADMIN);
+}
+
+bool User::is_admin() {
+    return this->type == UserType::ADMIN;
+}
+
+string User::toString() {
+    return email + " | " + username;
+}
+
+std::ostream& operator<<(std::ostream &os, User &user) {
+    os << user.toString();
+    return os;
+}
+
+void User::create(std::string &body, ContentType type) {
+    contents.emplace_back(body, type);
+}
+
+void User::print_questions() {
+    for(const auto &user : users) {
+        for(const auto &content : user.contents) {
+            if(content.type == ContentType::QUESTION) {
+                std::cout << user.username << ": " << content.body << std::endl << std::endl;
+            }
+        }
+    }
+}
+
+void User::print_content(int num) {
+    num %= contents.size();
+    std::cout << "Question " << num+1 << ": " << contents[num].body << std::endl
+              << "_______________________________" << std::endl
+              << "Answers:" << std::endl;
+    for(const auto &relation : contents[num].relations) {
+        if(relation->type == ContentRelationType::ANSWER_TO)
+            std::cout << relation->destination->body << std::endl;
+    }
+    std::cout << "_______________________________" << std::endl;
+}
+
+void User::edit_content(int num, string &body) {
+    num %= contents.size();
+    contents[num].body = body;
+}
+
+void User::delete_content(int num) {
+    num %= contents.size();
+    auto it = contents.begin();
+    it += num;
+    contents.erase(it);
 }
\ No newline at end of file
diff --git a/User.h b/User.h
index 6b239d9..276fafe 100644
--- a/User.h
+++ b/User.h
@@ -2,11 +2,11 @@
 
 #include <iostream>
 #include "AbstractUser.h"
+#include "Content.h"
 
 class User : public AbstractUser {
 public:
     User(string username, string password, string email, UserType type);
-
     static void init(const string &salt);
 
 public:
@@ -21,6 +21,23 @@ class User : public AbstractUser {
     static User& login(string username, string password);
     static User& signup(string username, string password, string email);
 
+public:
+    bool is_admin();
+
+public:
+    string toString();
+    friend std::ostream& operator<<(std::ostream& os, User& user);
+
+public:
+    vector<Content> contents;
+    void create(std::string &body, ContentType type);
+
+public:
+    static void print_questions();
+    void print_content(int num);
+    void edit_content(int num, string& body);
+    void delete_content(int num);
+
 private:
     static string salt;
     static vector<User> users;
diff --git a/main.cpp b/main.cpp
index 01eac03..9f557d6 100755
--- a/main.cpp
+++ b/main.cpp
@@ -1,8 +1,11 @@
 #include <iostream>
+#include <fstream>
 #include <string>
 #include "AbstractUser.h"
 #include "Exceptions.h"
 #include "User.h"
+#include "Logger.h"
+#include "Content.h"
 
 #ifdef _WIN32
 #define CLEAR "cls"
@@ -16,21 +19,27 @@ using namespace std;
 enum MenuState {
     START,
     LOGGED_IN,
+    QUESTIONS,
     END
 };
 
 int main() {
+    Logger::getInstance();
     User::init("SECRET_KEY");
     User * loggedInUser = nullptr;
     MenuState menuState = MenuState::START;
     string last_message;
-
+    bool show_logs = false;
     char choice;
+    int content_num = 0;
     while(menuState != MenuState::END) {
-        system(CLEAR);
-        if (!last_message.empty())
+        if(not show_logs)
+            system(CLEAR);
+        show_logs = false;
+        if (not last_message.empty()) {
             cout << last_message << endl;
-        last_message = "";
+            last_message = "";
+        }
         switch (menuState) {
             case MenuState::START: {
                 cout << "1. login\n2. signup\ne. exit\n";
@@ -43,8 +52,9 @@ int main() {
                             cin >> username;
                             cout << "Enter Password: ";
                             cin >> password;
-                            loggedInUser = &User::login(username,password);
+                            loggedInUser = &User::login(username, password);
                             menuState = MenuState::LOGGED_IN;
+                            _Log(*loggedInUser);
                         } catch (WrongUsernameOrPasswordException &e) {
                             last_message = e.what();
                         }
@@ -62,11 +72,7 @@ int main() {
                             loggedInUser = &User::signup(username, password, email);
                             menuState = MenuState::LOGGED_IN;
                             last_message = "User signed up!\n";
-                        } catch (UsernameAlreadyExistsException &e) {
-                            last_message = e.what();
-                            break;
-
-                        } catch (EmailAlreadyExistsException &e) {
+                        } catch (exception &e) {
                             last_message = e.what();
                         }
                         break;
@@ -83,10 +89,25 @@ int main() {
                 break;
             }
             case MenuState::LOGGED_IN: {
-                cout << "d.delete account\nl. logout\ne. exit\n";
+                if(loggedInUser->is_admin())
+                    cout << "s. show logs\n";
+                cout << "a. add question\nq. all questions\nd. delete account\nl. logout\ne. exit\n";
                 cin >> choice;
                 switch (choice) {
-                    case 'd': {
+                    case 'a': { // add question
+                        cout << "Enter your question: ";
+                        string question;
+                        cin.ignore(1);
+                        getline(cin, question);
+                        loggedInUser->create(question, ContentType::QUESTION);
+                        break;
+                    }
+                    case 'q': { // all questions
+                        content_num = 0;
+                        menuState = MenuState::QUESTIONS;
+                        break;
+                    }
+                    case 'd': { // delete account
                         try {
                             loggedInUser->deleteAccount();
                             cout << "Account successfully deleted\n";
@@ -98,10 +119,19 @@ int main() {
                         }
                         break;
                     }
+                    case 's': { // show logs
+                        if(loggedInUser->is_admin()) {
+                            system(CLEAR);
+                            Logger::getInstance().printLogs();
+                            show_logs = true;
+                        }
+                        else
+                            last_message = "Unknown Input\n";
+                        break;
+                    }
                     case 'l': { // logout
                         loggedInUser = nullptr;
                         menuState = MenuState::START;
-                        last_message = "GOOD BYE\n";
                         break;
                     }
                     case 'e': { // exit
@@ -114,6 +144,43 @@ int main() {
                     }
 
                 }
+                break;
+            }
+            case MenuState::QUESTIONS: {
+                loggedInUser->print_content(content_num);
+                cout << "p. previous question\nn. next question\ne. edit question\nd. delete question\nb. back to main menu\n";
+                cin >> choice;
+                switch (choice) {
+                    case 'p': { // previous question
+                        content_num--;
+                        break;
+                    }
+                    case 'n': { // next question
+                        content_num++;
+                        break;
+                    }
+                    case 'e': { // edit question
+                        cout << "Enter your question: ";
+                        string question;
+                        cin.ignore(1);
+                        getline(cin, question);
+                        loggedInUser->edit_content(content_num, question);
+                        break;
+                    }
+                    case 'd': { // delete question
+                        loggedInUser->delete_content(content_num);
+                        break;
+                    }
+                    case 'b': { // back to main menu
+                        menuState = MenuState::LOGGED_IN;
+                        break;
+                    }
+                    default: { // unknown input
+                        last_message = "Unknown Input\n";
+                        break;
+                    }
+                }
+                break;
             }
         }
     }