Forewarning: English isn't my first language, so I might make some spelling/grammar mistakes in English.
Very mild spoilers ahead, but its mainly about grammar.
It's nothing big, but I noticed a slight grammatical error in the beginning of Hiro's route. When the two unnamed german scientits speak, they say "Ha-ha! Hoffentlich er nicht explodiert wieder vor meinem gesicht", which gets the meaning across, but the proper way to say that would be to switch "explodiert" and "er nicht", to make the sentence "Ha-ha! Hoffentlich explodiert er nicht wieder vor meinem gesicht". The difference being the first one is a word for word literal translation, and the second one being adjusted for German grammar, as German grammar writes the verb before the subject. ill update this comment as I progress through his story with other German grammar errors.
Error 2: When Hiro says "Wenn Sie nicht gehen, ich werfe Sie raus". while the sentence is technically correct (for the most part, the same error of subject-verb switching happened at the end again), it translates to "When you don't go, ill Throw you out", which I guess could be the desired meaning, but I think its more common to say "If you don't go, ill Throw you out", which would be better communicated if he said something like "Falls Sie nich gehen, werfe ich Sie raus"
Error 3: When Hiro says "Mist! I-Ich Entschuldigung". This is once again a direct, word for word translation, which doesn't quite work the same in german. in German you don't say "im sorry"(at least not like that, the best way to say that would be "tut mir leid", which translates more to "causes me suffering"). you could say "sorry", or "sorry for me", which translate to "Entschuldigung" and "Entschuldigen Sie mich". the proper way to say what hes trying to say in this context would be either "Mist! Entschuldigung!", or "Mist! Tut mir leid". Either one would work fine in this context.
Error 4: When Hiro says "Was verdammt Sie machen hier, Herr Ratte?", which I assume is meant to translate to "What the fuck are you doing here, Mr. Rat?". outside of the same "subject-to-verb switching" error, the only other one would be that verdammt isnt used like that, a better substitution would be "um Teufels willen", which is a much more common phrase, meant to mean "by Devils will", similar to "um Gottes willen", which meant "by Gods will" (similar to the english phrases "what in gods name"). A better way to say what Hiro said would then be "Was, um (Teufels/Gottes) willen machen Sie hier, Herr Ratte?"
Error 5: When Hiro says "Ich muss sein negativ geladen. Wenn ich Kabel berühre, Kurzschluss den ganze Motor", which would be as if you said "I charged negatively must be. when I touch cables, short circuits the entire motor". Germans do a similar thing with descriptors, where the descriptors go before the noun. Anyways, the correct way to say the first sentence would be to say "Ich muss negativ geladen sein". The second one is a bit more tricky, as it does make sense, but isnt optimal. Theres two waiys to say that when he touches cabl;es, the motor short-circuits, Nr. 1 being "Wenn ich Kabel berühre, Kurzschluss ich den ganzen motor", which implies its his action to short cuircut the motors, and Nr. 2, "Wenn ich Kabel berühre, Kurzschlusst der ganze Motor", which would imply that it just kinda happens without his intention. id reccomend Nr. 2, giving us a final phrase of "Ich muss negativ geladen sein. Wenn ich Kabel berühre, Kurzschlusst der ganze Motor"
Error 6: When Hiro says "Auch wenn ich umdrehe Ladung, Kabel hat noch Elektrizität. Sie sind positiv geladen, Sie keiegen Schock nächster". The same mistake of putting the noun second is present in the first sentence, the sentence should be "Auch wenn ich die Ladung umdrehe, das Kabel hat noch Elektrizität". the second sentence is perfectly fine as far as i can tell, so the complete sentence would be "Auch wenn ich die Ladung umdrehe, das Kabel hat noch Elektrizität. Sie sind positiv geladen, Sie keiegen Schock nächster".
Error 7: When the Worker says "Der Chef sollte halt nicht versuchen, uns durch welche von seiner Art zu unterbieten". To be completely honest, I couldnt understand the second part of the sentence at all, and had to use google translate to understand it. Apparently its meant to mean that "The boss should not try to undercut us with some of his kind", which would be much better written by writing "Der Chef sollte halt nicht versuchen, uns durch seine sorte zu ersetzen".
That's all the ones I could find so far. I'm realizing now it might well just be a writing style choice to have Hiro make mistakes in German, but this doesn't feel like the type of mistakes someone would intentionally write into a characters speech. if I'm wrong, please let me know!