Is the dialogue idiomatic?

Two guys talk about a third guy. The third guy owns both a house and an apartment.

Guy 1: Is he still staying at the apartment for the most part?

Guy 2: Yes. It's closer to the woman he's been seeing.

Guy 1: I didn't know he was still seeing her. It must be serious then.

Guy 2: I think so.

1) Is the first statement natural? (in particular "staying" and "for the most part")

2) Is the rest of the dialogue idiomatic as well?