might i make a suggestion? no matter how much something may look like a defined line, it never is. its all shadows and light. as soon as you add a black line to a drawing it flattens it. you shaded very well, so now try it without putting those solid lines in.
it will feel wrong and takes getting used to but you get a better, more realistic piece in the end. other than that nice work. well on your way
looks good man keep it up but yeah soul products is right, and like my life drawing professor said draw by shadowing not by the outlines but then again this might all be on purpose so good job man this looks amazing