Hello

Is it somehow possible to make the user is logged out automatically when the forum is closed?

No, that would not work, because the statelessness of the HTTP-protocol. If you klick a link or you press the enter-button on your keyboard after inserted a URL the browser sends a request to the webserver and get ressources (the page, images, css and javascript scripts) in return. After that moment the connection between your browser and the webserver is closed. The webserver will not take any notice, that you closed your browser window or tab or you leaved the page onto another goal.

The easy but time consuming way is to log out in every forum after every single session and log in explicitely for the next session again. The more complicated but afterwards easier way is to ensure different names for the cookies of every single forum with the prefixes of their names.

I don't know if mlf2 gives you such a setting. The setting session_prefix (Admin=>forum settings=>advanced settings) may be a starting point.

I disabled the auto login and changed the advanced settings "remember_last_visit" and "remember_user_data" from 1 to 0...

The settings remember last visit and remember user data controls the lifetime of the cookies (current session or x days) and auto_login is logged in if he requests one of the forum pages. If mlf2 handles different cookie names (cookie prefixes) you can reenable these settings.

Tschö, Auge