Translation:What were you talking about with my neighbors?
Is there a reason why most of the time czech past is translated as past progressive rather than past simple? It would seem to me that "What did you talk about with my neighbours" has exactly the same meaning.
I thought at first it was just an oversight, but now I wonder if it's maybe due to the perfective/ imperfective verbs?
I hope I'm right, I'm Croat and this is the reason in Croatian, it should also work out for Czech: Slavic languages have specific way of expressing verbal aspect, here verbs often occur in pairs, with two related verbs being used respectively for imperfective and perfective meanings. In English you use different verb tenses to express the duration; for example I talked to my neighbours (short) /I was talking to my neighbours (long). But in Czech (and other Slavic languages) verb "mluvit" means to talk for a long time and that's why we translate it as "was talking, have been talking, etc." I don't know how to say that you talked to someone for a short amount of time, but I truly hope this helped and that I'm right.
Mými is "my." See, for example: https://en.wikipedia.org/wiki/Czech_declension#Possessive_pronouns.