Not sure if you still want to work on it, but you really went foreward with flawed lines. Pauls' pose on the bull is all wrong, it looks wrong and makes little sense. He doesn't look like he is sitting on there, rather like he is being bucked foreward awkwardly. In your initial sketch I can see you wrote "tilt back" but you didn't tilt back, and I think the problem is severe enough for the lines to be redone. Consider also the pose of his arms, they are nonsensicle. His grip on the reign is upside down, and his axe is raised for no reason. A sturdy pose would have him sitting back on the bull, a palm down grip on the strap, and a lowered axe.
Look at this girl riding a horse: