-괜찮아. 너는?

That's okay. What about you?

=> Another way: Your sentence is okay and this is another way of saying it.

​Not bad, How about you?

-나 심심해.

I'm board. --> I'm bored.

=> Corrected spelling.

-이번 일요일에 뭐 할거니?

What are you doing on Sunday? 

=> Another way: Your sentence is okay and this is another way of saying it.​

What are you going to do this Sunday?​