Please correct my sentence in Chinesee

A: Are you busy or not this evening?
　　你今天晩上忙嗎？

B: I have things to do this evening. I am available tomorrow evening.
　　我今天晩上有事儿。我明天晩上没有事儿。

A: Does your big brother have a girlfriend or not?
　　你大哥有没有女朋友？