diff --git a/.gitignore b/.gitignore
index 0d019fc..005a1ab 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 .vscode/
-config.php
\ No newline at end of file
+config.php
+test.php
\ No newline at end of file
diff --git a/Session.class.php b/Session.class.php
index 7b96477..790c401 100644
--- a/Session.class.php
+++ b/Session.class.php
@@ -3,8 +3,19 @@
 session_start();
 
 require_once("Database.class.php");
+require_once("constants.php");
 
 class Session {
+    public static function get_admin_session()
+    {
+        return Database::escape_string($_SESSION[$GLOBALS["SESSION_ADMIN"]]);
+    }
+
+    public static function get_visitor_session()
+    {
+        return Database::escape_string($_SESSION[$GLOBALS["SESSION_VISITOR"]]);
+    }
+
     public static function generate_id()
     {
         return uniqid(uniqid("", true), true);
@@ -13,33 +24,54 @@ class Session {
     public static function login($user_id)
     {
         $session_id = self::generate_id();
-        $_SESSION["gastoadmin"] = $session_id;
+        $expiry = time() + $GLOBALS["SESSION_ADMIN_VALIDITY"];
+        $query = "INSERT INTO `user_sessions` (`session_id`, `user_id`, `expiry`) VALUES ('$session_id', $user_id, $expiry);";
+        Database::execute_query($query);
+        $_SESSION[$GLOBALS["SESSION_ADMIN"]] = $session_id;
+        return self::is_logged_in() == $user_id;
     }
 
     public static function logout()
     {
-        unset($_SESSION["gastroadmin"]);
+        $query = "DELETE FROM `admin_sessions` WHERE `session_id` = '" . self::get_admin_session() . "';";
+        Database::execute_query($query);
+        unset($_SESSION[$GLOBALS["SESSION_ADMIN"]]);
     }
 
     public static function is_logged_in()
     {
-        $query = "SELECT `user_id` FROM `visitor_sessions` WHERE `session_id` = '" . $_SESSION["gastroadmin"] . "';";
-        Database::execute_query($query)
+        $query = "SELECT `user_id` FROM `admin_sessions` WHERE `session_id` = '" . self::get_admin_session() . "';";
+        $result = Database::execute_query($query);
+        if ($result->num_rows == 1) {
+            return $result->fetch_assoc()["user_id"];
+        }
+        return false;
     }
 
     public static function remember_visitor($visitor_id)
     {
         $session_id = self::generate_id();
-        $_SESSION["gastroguest"] = $session_id;
+        $expiry = time() + $GLOBALS["SESSION_VISITOR_VALIDITY"];
+        $query = "INSERT INTO `visitor_sessions` (`session_id`, `user_id`, `expiry`) VALUES ('$session_id', $visitor_id, $expiry);";
+        Database::execute_query($query);
+        $_SESSION[$GLOBALS["SESSION_VISITOR"]] = $session_id;
+        return self::get_visitor() == $visitor_id;
     }
 
-    public static function get_visitor($visitor_id)
+    public static function get_visitor()
     {
-        # TODO
+        $query = "SELECT `visitor_id` FROM `visitor_sessions` WHERE `session_id` = '" . self::get_visitor_session() . "';";
+        $result = Database::execute_query($query);
+        if ($result->num_rows == 1) {
+            return $result->fetch_assoc()["visitor_id"];
+        }
+        return false;
     }
 
     public static function forget_visitor($visitor_id)
     {
-        # TODO
+        $query = "DELETE FROM `visitor_sessions` WHERE `session_id` = '" . self::get_visitor_session() . "';";
+        Database::execute_query($query);
+        unset($_SESSION[$GLOBALS["SESSION_VISITOR"]]);
     }
 }
\ No newline at end of file
diff --git a/Setting.class.php b/Setting.class.php
index d4af3b5..fff3b8f 100644
--- a/Setting.class.php
+++ b/Setting.class.php
@@ -10,18 +10,21 @@ class Setting {
         $this->settingKey = Database::escape_string($setting_key);
     }
 
-    public function get($default="")
+    public function get($default="", $set=false)
     {
         $query = "SELECT `setting_value` FROM `settings` WHERE `setting_key` = '" . $this->settingKey . "';";
         $result = Database::execute_query($query);
         if ($result->num_rows == 1) {
-            return $result->fetch_assoc()["setting_key"];
+            return $result->fetch_assoc()["setting_value"];
          } else {
              if (!empty($default)) {
+                 if ($set) {
+                     $this->set($default);
+                 }
                  return $default;
              }
-            return false;
          }
+        return false;
     }
 
     public function set($value)
diff --git a/Template.class.php b/Template.class.php
index 91899e6..0d0175a 100644
--- a/Template.class.php
+++ b/Template.class.php
@@ -222,7 +222,11 @@ class Template
      * @uses      $template
      */
     private function replaceLangVars($lang) {
-        $this->template = preg_replace("/\{L_(.*)\}/isUe", "\$lang[strtolower('\\1')]", $this->template);
+        $this->template = preg_replace_callback("/\{L_(.*)\}/isU", 
+        function($matches) use ($lang) {
+            return $lang[strtolower($matches[1])];
+        },
+        $this->template);
     }
 
     /**
diff --git a/User.class.php b/User.class.php
new file mode 100644
index 0000000..4541ae9
--- /dev/null
+++ b/User.class.php
@@ -0,0 +1,61 @@
+<?php
+
+require_once("Database.class.php");
+
+class User 
+{
+    private $user_id = null;
+
+    public function __construct($user_id)
+    {
+        $this->user_id = $user_id;
+    }
+
+    public function id() {
+        return $this->user_id;
+    }
+
+    public static function authenticate($username, $password) 
+    {
+        $escaped_username = Database::escape_string($username);
+        $query = "SELECT `password`, `user_id` FROM `users` WHERE username='$escaped_username';";
+        $result = Database::execute_query($query);
+
+        if ($result->num_rows == 1) 
+        {
+            $user = $result->fetch_assoc();
+            if (password_verify($password, $user["password"]))
+            {
+                return new self($user["user_id"]);
+            }
+        } 
+        
+        return false;
+    }
+
+    public static function register($username, $password, $admin=false)
+    {
+        $escaped_username = Database::escape_string($username);
+        $hashed_password = password_hash($password, PASSWORD_DEFAULT);
+        $admin_status = (int)$admin;
+
+        if (!password_verify($password, $hashed_password))
+        {
+            die("Something went wrong trying to hash the password...");
+        }
+
+        $query = "INSERT INTO `users` (`email`, `password`, `is_admin`) VALUES ('$escaped_username', '$hashed_password', $admin_status);";
+
+        if (!Database::execute_query($query)) {
+            return false;
+        }
+
+        $id_query = "SELECT `user_id` FROM `users` WHERE `email` = '$escaped_username';";
+        $id_result = Database::execute_query($id_query);
+
+        if ($id_result->num_rows == 1) {
+            return new self($id_result->fetch_assoc()["user_id"]);
+        }
+        return false;
+    }
+}
\ No newline at end of file
diff --git a/constants.php b/constants.php
new file mode 100644
index 0000000..b8cdd52
--- /dev/null
+++ b/constants.php
@@ -0,0 +1,6 @@
+<?php
+
+define("SESSION_ADMIN", "gastroadmin"); # Name of the admin user ID variable in sessions
+define("SESSION_VISITOR", "gastroguest"); # Name of the visitor ID variable in sessions
+define("SESSION_ADMIN_VALIDITY", 300); # Lifetime (in seconds) of admin sessions
+define("SESSION_VISITOR_VALIDITY", 86400); # Lifetime (in seconds) of visitor sessions
\ No newline at end of file
diff --git a/index.php b/index.php
index 7184c96..60f840b 100644
--- a/index.php
+++ b/index.php
@@ -8,6 +8,10 @@ Route::add('/',function(){
     include("views/index.php");
 });
 
+Route::add('accounts/register/', function() {
+
+}, "post");
+
 Route::run('/');
 
 ?>
\ No newline at end of file
diff --git a/language/de/main.php b/language/de/main.php
new file mode 100644
index 0000000..e69de29
diff --git a/sql/schema.sql b/sql/schema.sql
index 7387791..4fa4567 100644
--- a/sql/schema.sql
+++ b/sql/schema.sql
@@ -9,7 +9,6 @@ CREATE TABLE IF NOT EXISTS `users` (
     `display_name` VARCHAR(255),
     `email` VARCHAR(255) NOT NULL UNIQUE,
     `password` VARCHAR(255) NOT NULL,
-    `salt` VARCHAR(255) NOT NULL,
     `is_admin` BOOLEAN,
     PRIMARY KEY (`user_id`)
 );
@@ -17,9 +16,9 @@ CREATE TABLE IF NOT EXISTS `users` (
 CREATE TABLE IF NOT EXISTS `user_sessions` (
     `session_id` VARCHAR(255) NOT NULL,
     `user_id` INT NOT NULL,
-    `expiry` DATETIME NOT NULL,
+    `expiry` INT NOT NULL,
     PRIMARY KEY (`session_id`),
-    FOREIGN KEY (`user_id`) REFERENCES `users`(`user_id`)
+    FOREIGN KEY (`user_id`) REFERENCES `users`(`user_id`) ON DELETE CASCADE
 );
 
 CREATE TABLE IF NOT EXISTS `locations` (
@@ -34,17 +33,17 @@ CREATE TABLE IF NOT EXISTS `permissions` (
     `location_id` INT NOT NULL,
     `is_owner` BOOLEAN,
     PRIMARY KEY (`user_id`, `location_id`),
-    FOREIGN KEY (`user_id`) REFERENCES `users`(`user_id`),
-    FOREIGN KEY (`location_id`) REFERENCES `locations`(`location_id`)
+    FOREIGN KEY (`user_id`) REFERENCES `users`(`user_id`) ON DELETE CASCADE,
+    FOREIGN KEY (`location_id`) REFERENCES `locations`(`location_id`) ON DELETE CASCADE
 );
 
 CREATE TABLE IF NOT EXISTS `visits` (
     `visit_id` VARCHAR(255) NOT NULL,
     `location_id` INT NOT NULL,
-    `arrival` DATETIME NOT NULL,
-    `departure` DATETIME NOT NULL,
+    `arrival` INT NOT NULL,
+    `departure` INT NOT NULL,
     PRIMARY KEY (`visit_id`),
-    FOREIGN KEY (`location_id`) REFERENCES `locations`(`location_id`)
+    FOREIGN KEY (`location_id`) REFERENCES `locations`(`location_id`) ON DELETE CASCADE
 );
 
 CREATE TABLE IF NOT EXISTS `visitors` (
@@ -61,13 +60,13 @@ CREATE TABLE IF NOT EXISTS `visitors` (
     `phone` VARCHAR(255),
     `email` VARCHAR(255),
     PRIMARY KEY (`visitor_id`),
-    FOREIGN KEY (`visit_id`) REFERENCES `visits`(`visit_id`)
+    FOREIGN KEY (`visit_id`) REFERENCES `visits`(`visit_id`) ON DELETE CASCADE
 );
 
 CREATE TABLE IF NOT EXISTS `visitor_sessions` (
     `session_id` VARCHAR(255) NOT NULL,
     `visitor_id` VARCHAR(255) NOT NULL,
-    `expiry` DATETIME,
+    `expiry` INT,
     PRIMARY KEY (`session_id`),
-    FOREIGN KEY (`visitor_id`) REFERENCES `visitors`(`visitor_id`)
+    FOREIGN KEY (`visitor_id`) REFERENCES `visitors`(`visitor_id`) ON DELETE CASCADE
 );
\ No newline at end of file
diff --git a/views/index.php b/views/index.php
deleted file mode 100644
index 2c0beb6..0000000
--- a/views/index.php
+++ /dev/null
@@ -1,27 +0,0 @@
-<?php
-
-if (!defined("GastroData")) {
-    die("This file cannot be accessed directly. Sorry.");
-};
-
-require_once("Template.class.php");
-require_once("Setting.class.php");
-
-// Das Template laden
-$tpl = new Template();
-$tpl->load("index.tpl");
-
-// Die Sprachdatei laden
-$langs[] = "de/lang_main.php";
-$lang = $tpl->loadLanguage($langs);
-
-// Platzhalter ersetzen
-$title = new Setting("title");
-$tpl->assign( "website_title", $title->get("GastroData") );
-$tpl->assign( "time",          date("H:i") );
-
-// Zugriff auf eine Sprachvariable
-$tpl->assign( "test",          $lang['test'] );
-
-// Und die Seite anzeigen
-$tpl->display();
\ No newline at end of file