I noticed the path to the script was:
/home/t/timeflash.de/public_html/cgn/cpg143/bridge/woltlab21.inc.php
I'm curious which plan you are on since this does not appear to be the typical path for the shared linux plans which are generally /home/cpanelusername/public_html. And since that path was generated by PHP, I'm assuming that it really is where the script is located. Are you on a dedicated plan by some chance? Or is this not hosted with LP? Just trying to get an idea as to what the directory structure are on the server you are on.
It might also help to know what the path is to each of the various parts... eg. what is the path to your forum, to the bridge files, to the config.inc.php, etc?