Something is causing the translations to revert back to English on Help:VisualEditor/User guide/de. The English version doesn't appear to be missing any <translate> tags, but the first edit I made changed dozens of messages (which is strange, since I was using Special:Translate, and that only allows translation of a single message). Also, Fuzzybot restored the English messages after you reverted them. Am I missing something obvious here, or is this a problem with the source page?
Topic on User talk:Kghbln
Ouch, this indeed seems to be a bit messy. Admittedly I am not longer familiar with the translation interface etc. Perhaps there is a bug in the software or something else went wrong while administering the translations. It is probably best to ask one of the translation administrators for guidance and help.