Have they painted the garage yet?

No, they haven't. He is still painting it.

How long have they been painting it?

They have been painted it since he returned from a business trip.

When did he return from his business trip?

He returned a week ago.

What were they painting when he returned from the trip?

They were painting the walls in the garage.

— .Have they painted (to paint) the garage yet?

— No, they havent . He is still painting (to paint) it.

— How long have they been painting (to paint) it?

— They  have  been painting (to paint) it since he returned from a business trip.

— When did he return (to return) from his business trip?

— He returned (to return) a week ago.

— What were they painting (to paint) when he returned from the trip?

— They were painting (to paint) the walls in the garage.