Chatting can be hard even in a person's native language. Some good topics to learn vocabulary for are common weekend activities.... such talking about movies or sporting events. Then, you can always talk about the weekend.
If it is Monday or Tuesday, you can ask, "What did you do this weekend?"
If it is Thursday or Friday, you can ask, "Do you have any big plans for the weekend?"
If it is Wednesday, then you can talk about how the week is halfway over. Or ask, "How's you're week going?"