I did not want to admit it, but it caught me just: AFTER THE UPDATE WITH THE CONTENT MANAGER GERMAN LANGUAGE NO MORE.
Getting e-mail to support, the need to know this problem long ago. Quick response: Here the missing file. I could tell by the size of it already, that this could not possibly be anything. File copy (good IT skills urgently required !!!), but now I had only the German text in English. Again E-mail to support. The answer now lasted one day, then again: Here the missing (plural!) Files. Again, just did not fit the size again. After copying it was now German text with an unfamiliar language. A change was not possible.
Luckily I had the above backup. So partly filled with backup, and update the Content Manager performed again. Now it worked. A review on the Navi showed me that I know the support had not sent all the necessary files. And after two emails. That annoyed me properly. From now on it can only get better?