Hi LeonidS any many thanks for your help! I understood and choosed the way ranslating the xml-files because I can use for other installations too.
I also found the way to "import" the files / changes by the developer - module. OK so far. But It doesnt import / update all the values from the xml-file. In my case it doesnt import changes in the /system/mylanguage.xml - file. For example: trying to add a comment to any post, in the opening form it is nearly all in english ("leave messga here" ... choose the visibility (Only me, friends, ...) everything in english. In my xml-file everything is translated.
Do you have any idea how to fix? And yes: I looked in the Polyglott regarding this values: they are in english in the dadabase. So obviousely my translations were not imported?!
Thanks for youre help!
Walhalla