I think you are doing great.
Skeletors left hand is great, hands can be tricky and He-man has a firm stand on the ground.
You are studying well.
My personal advice would be to elongate the arms and legs a little bit. Itīs a common thing to give the persons a more mature feeling. Your proportions seem to be right but would be used for childrens body types.
I think youīll be an amazing artist!