Is 't posible to créate an private forum with the admins of the website? So only the user (after login) and the website admin can see there topics and messages? 

The admin can of course see everything from all users. I know you can set users in groups but I want every user can't see the messages from other users.  And you can set a a new topic to Private. But can you set that automatic? So the user doesn't have to think about that.