Setting: Modern day, if that makes any sort of difference.
So I have a character who is a native German speaker going to college in America. He's mostly fluent and knows some slang (because I am sure he's watched American movies and TV, and he's been going to college at this point for three years). Are there any common grammatical mistakes he might make or words he might mix up? I know, for instance, from my many years of taking French, that native French speakers tend to give words a "the" when a native English speaker wouldn't, or end a question with a yes/no ("You enjoy the tennis, no?"), because that's how it works in French and they're making a literal translation in their head. (And I know I make similar mistakes in French, though I have no idea what they are.) But since I've never met or had a prolonged conversation with a native German speaker, I have no idea what sort of verbal irregularities they might have besides an accent.
Help? I don't even know how one would hypothetically google this puppy.
I'm writing a story in which one of the characters is a young man from Beijing who has been alive, in a sort of alternate plane, since about 1750. He was from a wealthy merchant family and was studying for the imperial examinations when he was kidnapped and brought to the aforementioned alternate plane. He has kept up with the changes in written Chinese through reading books and newspapers, so he is familiar with the grammar/syntax/vocabulary of modern mandarin, but he has never spoken it or heard it spoken. So my question is: how would his spoken Chinese sound to a modern young man from a major city? (I'm thinking the boy is from Xi'An, where in my experience the putonghua is pretty standard sounding.) Would he just have an especially thick er hua? Was there a Chinese equivalent of a great vowel shift that would make his accent sound funny? Is there a tonal difference between beijing dialect circa 1750 and modern mandarin? I've googled Beijing dialect, Beijing hua, lao Beijing hua etc., but mostly gotten info about Beijing specific vocab, which he would know is not in common use from reading modern newspapers. My question is mainly A., would he have any accent peculiarities that a modern beijinger would not have, and B. would it sound archaic to the modern guy from Xi'An, or would it just sound like he was from some hick town in dong bei? I'll be super grateful to anyone who might be able to help me out on this!