I think you've really gotten the general forms well, the only improvements would really come with time and practice. I'd just say maybe not FILL the drawings? As in, if I'm assuming correctly, the sketches are for capturing form, so for that, you don't really need to fill/color the sketches in any way. Focus on quantity and timed works rather than a full work of art. That yields results the quickest.
you seem to have a really good idea of the form of the human body, but one thing I noticed is that it all seems to fit together kind of... loosely, for lack of a better term. Maybe it would be helpful to study the exact musculature on the body so that the form can fit together more tightly.