Structure sentence - Are you sure..?

I. EXAMPLES:-

Are you sure? [listen]

Are you sure about that? [Listen]

Are you sure of what you said? [Listen]

Are you sure that he is not coming? [Listen]

II. DIALOGUES:-

A: I’ve had so many problems with my new car. It’s driving me crazy.

B: Are you sure you don’t want to buy a new one?

A: How can I? I already spent a lot of money on this one.

B: I guess you’ll be spending a lot of money on repairs then.

A: I guess so. Unless you want to buy the car.

B: No, thanks. I don’t think I’d want to buy your car. It has too many problems.

A: I don’t blame you. It’s a piece of junk.