have you watched his robo bean and gesture videos? watch them. definitely. hes also got like a whole series on anatomy. just watch the entire figure drawing and anatomy series hes got, if you havent. watch it again if you have.
the pelvis youve drawn on the model is too small and the wrong shape, and your spine is in the wrong place. its harder to realise with the clothing, but theres a twist to this pose, so the spine wouldnt go straight down the body like that. also, your ribcage needs more form - look back at prokos and see how he draws the actual shape of the ribcage, not just a circle.
you could really do at looking again at the gesture videos, because your exaggeration of the pose doesnt exaggerate in the right areas, and breaks the pose. you dont need to yank that leg up that high. instead, increase the curve of the spine, dont draw it practically straight. draw the curve of the neck, capture that motion and jump in the legs, and the overall lean to the right.
i realise people have said a lot of this already, but also: practice drawing with smoother, flowing strokes, and less hairy, because it makes the gesture clearer and stronger.
its good that youre trying to improve your art, and youre looking in the right directions. proko is definitely a good way to do that. keep up the hard work!