Zu volle \hbox (0.7029mm zu breit) im Absatz in den Zeilen 140--140

Does it really help to translate the error messages if command names
are still based on english as in horizontal box here?

This is a straight question, I do not mean to imply that it should
not help, it is rather hard to tell if your first language is english

It probably does not make sense to start translating command names
from pseudo-english to pseudo-german as where would it end, every
contributed package needing to be customised for every language?

> For TeX this should be simple; a change file should suffice.
> But for LaTeX? The messages are hardcoded into the kernel... :-(

take a look at the autoload version, you'll find most of the LaTeX
error texts in the external file autoerr.sty of course if they are in
an external file, they could in principle be changed......
but I am still not sure its a good idea:-)