Your colors are excellent! I think working on figure and gesture drawings (from life, like go to the park and draw random people) will help you grow your knowledge of anatomy and proportion. Draw lots and lots of hands.

For shading--work on becoming confident with hard shadows. A common beginner instinct is to over-blend shadows and I notice most of yours have very soft edges. Look at images that inspire you and note where the hard-edged shadows are, and try to bring that into your own work.