Authors who are unable to check their foreign languages annoy me to no end. I once read a book where the heroine ordered a hot chocolate with whipped cream in Vienna, only the author had just run the sentence through google translate without cross-checking it with a German speaker so she ended up with 'eine heiße schokolade mit gepeitschter creme' which was so hilariously wrong that it made me laugh out loud in the middle of the night XD
But this is even worse because you could actually have found these things in a dictionary/google translate without the help of a native speaker.
Your example is hilarious, and my German isn't even that good. ;) Indeed, I think it is very sloppy but I don't think authors realize enough that their books will also be read by people who do understand a language. It often looks cool to implement things from foreign languages (especially in the English-speaking world as knowing multiple languages is quite rare there) but please check the things you write down.
But this is even worse because you could actually have found these things in a dictionary/google translate without the help of a native speaker.