why it means "you talk to us?" rather than "we talk to you?"
Note that, in formal French, a question is structured as ‘object verb-subject?’. You can easily identify that it’s a formal construction because of the hyphen and the pronoun at the end of the question. Also, note that ‘parlez’ is the vous-conjugation of ‘parler’, indicating that ‘vous’ is the subject of that question. Therefore, a question ending with ‘parlez-vous ?’ is translated as a question beginning with ‘do you talk’ or ‘are you talking’. Since ‘nous’ is the verb object, ‘nous parlez-vous ?’ can be translated as ‘do you talk to us?’ or ‘are you talking to us?’