I changed the menu a bit to ad a contact button and some cosmetics, at the same time I changed the FileMgmt lang translation dounloads word to upper case. Now I can not go back to the old setting nor login or out as Admin. I get this message:
here
Anyone knows how to fix this. I repeat that I allready tried to set it back the way it was but the errors continue.
I am still able to log in by cookie recognition only so far, but not by using the panel. (Just when I finished everything almost, one more problem vaused by me.
Thank you.

Looks like you have whitespace at the beginning of the file management's language file. Make sure that there's nothing in the file preceding the opening PHP tag (i.e. no empty lines, no spaces).

bye, Dirk

That was it! there was thtml script before the opening PHP code. Thank you Dirk.