Okay - with the line:
chdir("../../forum/");
it seems to work. Instead of an error I got a "done" :up:
(yaah, I moved the filders with putty on my mobile. No bash command completion - everything by hand

)
Now there is the Problem, that I don't find the groups... Everything is turned on in the user rights, also the groups are activated in the admincp-groups-general settings.
But I found:
Strings To Find In "viewthread.php"
These are the strings to find in viewthread.php. Each replacement is seperated by a space followed by a comma.
Is there anything more to replace in a php file?
I need to go home, there is the manual

Hopefully it helps!
Thanks for the hints!!