The sideways run also feels like a diagonal run because the far (black) buttock is consistently visible to the left of the front (grey) buttock.
The torso should move up and down with the run, as when the legs are extended, they're not pushing it upward. The lack of vertical motion may be what your friend meant about bending the knees more.
It may help you to draw the floor underneath the figure so that you can position the feet in a way that makes sense, as well as add a simple torso so you can more easily track its motion and rotation.