Great attempt, better than anything I've taken a swing at.
Though the chest is a bit like a wooden plank. There's probably someone much more experienced with animation who could give better advice, but from what I can tell, having the last frame stick for a moment with an entirely static image makes it look really choppy. And it's not as much of an issue, but work on the anatomy a little bit, I don't think legs bend like that xD
Quite right. I made some minor changes so that the bend isn't as severe and there's one less frame.