1. Everyone is having a lot of fun. 2. Although I agree with "that makes sense," or more literally, "that adds up," this is used often with a tone of annoyance and sometimes irony...like if you go buy sometime because it is on sale very cheap and then try to use it and it breaks, you might say that figures. Or if someone you don't like does something which annoys you. Essentially, it is not surprising (usually because you did not expect much to begin with). 3. There is a lot left to be done.

1. Everyone is enjoying themselves (like they were at a party) 2. That makes sense (from 'figure something out) 3. We haven't looked at something very closely (we have admired the paintwork, but we don't know what's underneath)

1. "Everybody's having a ball" - having a ball is having fun. 2. "Figures" - to calculate, to find out, body shape if it is used as a noun. For example: - How do you figure it out? - She has a nice figure ! 3 ."We haven't scratched the surface" - means we don't know what is behind the scene.