This already looks really good! Your forms are really good and solid, you simplified it well and the proportions are also good. The main issue here in my opinion is the perspective. This is a really dynamic pose. We look at him from above so the legs are not as long as they would usually be. Even though he is bending them we still see them from above. Because of this parts of the calfs are hidden as well. The head is tricky but if you look closely you’ll notice that we can see the top of his head so the top plane for the head should be visible. A good way to see how the box is tilted are the eyes. Draw a line through them and you will have the general direction of one plane of the box. You already did an amazing job, keep it up and I hope this helps you :)
