I can see a lot of improvement. To improve even further i feel like should try out different approaches to drawing the human body. I would suggest you to try looking at your reference as an abstract shape (partly closing your eyes can be helpful). The second tip is to try to measure the distances between the shapes.
I feel like you should try to stylize less your figures, because if you truly want to understand the anatomy, it is better to capture the image the most realistically as you can. Tip : flip the page over and outline your realistic figures and then stylize them.
A way to practice: Another good exercise is to take only 1 minute drawing session (draw the poses big). After you drew the 1 minute pose, hide it. Then take a muscle anatomy reference and try to add in the muscles to your drawing (that is why you needed to draw the poses big). After addinhg the muscles, look at the figure again and try to find mistakes.
PS: Simplify the whole body in one huge abstract shape. Then carve out smaller shapes (at this point it is still really easy to correct some disproportions. Add the details in the very end and only if it would be neccessary, sometimes the drawing looks great on itself.