1.我不相信 I don't believe it./Nal, I don't buy it.
A: I heard that Paul is dating Sarah.
B: No, I don't believe it.
2.你说真的？ Really?/Seriously?/Are you sure?
A: The Chinese National Soccer made it to the World Cup!
B: Are you sure?
3.你开玩笑呢吧？ Are you kidding?/Are you kidding me?/You gotta be kidding me.
A: Mary is crying loudly outside!
B: Are you kidding?
4.不可能！ No way./No shit./Are you shitting me?
A: I am going to eat dinner with Mary.
B: Are you shitting me?