The german translation of Plone Core (plone.app.locales) is under reviewing. Jörg Zell, Mike Derstappen and me put careful effort on it during Salt Lab Sprint and the days after.
There is wording to think about, to be modernized and afterwards to fix in the guidline terms-de.txt . Not much but some.
You are welcome to comment our translations!
See here for my summary of points to be discussed: https://github.com/collective/plone.app.locales/pull/237#issuecomment-429638793