"Do they know us?"
Translation:Czy one nas znają?
Yes, that sounds weird. I'm afraid that similar constructions may be accepted somewhere, but I don't think they should.
You can look at it like that: "Czy" is optional, and if you omit it, you end up with "Nas znają?", which is very strange and means something along "What? It is us that they know?!"
"Znają nas?" on the other hand, is perfectly fine. But a pronoun shouldn't be put at the end of the sentence if it can be avoided. Here, it can't, as mentioned above. But specify the subject, and it already should be "Oni nas znają?"
You should avoid putting the pronoun at the end of the sentence.
And if you want to put it, I think you should state the subject more clearly (Czy oni/one znają nas?), but that's still not recommended - although this one is accepted.
Generally, it looks as if you stressed US strongly.
Ok. Sorry I’m not communicating clearly. Yes. That was the answer I had typed previously: Czy nas znają? So when it was denied, I came to the discussion section and read your first comment and I concluded you were saying that it was abnormal so it would not be accepted. Thank you for the update.