It depends on what they need help with.
Of course.
I'd be happy to.
It would be my pleasure.
Sure. What do you need help with?
I can try!
I'm sorry -- I can't right now.
I'm sorry -- I have a bad back. (Let's say that want you to help move a heavy item.)
I could later, but not now. Would that work?
This is a bad time. Is there another time we could do it?
I'm sorry -- I don't know anything about that.
I'm sorry -- I'm new here too and just don't know.