The game uses always the same data directory in the computer independent of version, so different versions will write on the same files. Once the save is updated to the next version, it cannot be updated back and is not ensured that it will work on previous versions, most of the time, it will probably crash the previous version because new versions often add new data to the save that previous versions do not support, so the save update tool is only meant for upgrading and not downgrading :).
Regarding the German translation, I can pass on the feedback, but the translations haven’t been updated in a while, it might take some time to have them brought up with fixes.