Thanks for your answer!
I changed both system and apache to non UTF-8 and all is well now.
I do have one other problem now. I am running Drupal with the fileshare module which has a ajax way of displaying local folders on the server. Now some of the directory's are labled "Gehäuse" and its not displayed correctly (same problem as before). I guess this is a PHP problem not have the correct encoding.
Do you know how to enable this kind of encoding in PHP?