I always break it down to simple 3d shapes.
You can do it more complicated like in the example above or
more simple. First trace over the reference and draw countour
lines over it, that makes it easier to imagine the direction of the
planes. Then hand draw the simple shapes, opacity down and
draw the shoe over it.
I tried to keep your style for the drawing of the shoes.
I do think that the shoes that you drew fit to your current level + style,
I wouldn´t worry about it and get better at it with time
