Formal
Are you kidding?: 농담하세요?
Why are you so: 왜 그렇게..
I don't want to hear you: 듣고 싶지 않아요

informal
장난해?
왜 그렇게..
듣기 싫어

Are you kidding? =  너 장난하니?

Why are you so = 너 왜 이렇게..

I don't want to hear you = 너한테서 듣고 싶지 않아.

note: these are all informal.