This is very good. You should join my contest. The body shape here is almost exact to my character. ( who you would need to draw for the contest. ) I think you would do a splendid job if you entered! The first place prize is $200 or 16,000 [link]
If you want to study shading and shadows, just pay attention to your surrounding and at night look at your hand, the light strangely reflects on all sides of it until the light is out of reach. Just don't look at the hand much because it will mess up everything you have learnedabout shadows. You don't need to go to a class to learn about shadows and shade.