@mil3s, Overall you did an excellent job, met most of the fundamentals but there are a few minor things i noticed. I've attached an image where i did annotations for a better understanding.

Amazing job, @mil3s! I agree with @Christopher Beaven, the proportions don't need to be perfect (even though I think you did great with that). I also love the way you've used your hatch marks, they really help describe the volumes effectively and pleasingly. I'd add up just one little extra note to @Steve Lenze's shrewd critique by suggesting that you could perhaps try to vary some more the quality of the shading edges. The photo of the plaster cast shows a wide range of hard, soft and lost edges, while, in your drawing, everything looks a lot more hard and angular. As a personal shading style in a creative art piece, I actually think it looks pretty cool (as I mentioned, I really like the feel of the hatch lines). But if this drawing is an observational study which is supposed to be focused on light and value (as I'm assuming it is), I'd say it could be very helpful for you to notice those edge variations and try to bring them more into your drawing. For example, one of the areas that calls my attention the most regarding this issue is the large groove to the left of the eye (our left): there's a transition from the deeper shadow to the reflected light above it which, in the object, looks very soft, but happens to have a very defined and sharp edge in your drawing, and this makes that plane change feel blocky rather than rounded. Softening the value edge some more (as Steve did in the paint-over the provided you) could help better show that groove area as a rounded form. The same suggestion applies to any other areas in the drawing where you notice the forms should look more rounded than blocky. Hope this helps! If you have any questions, please just let me know. Keep up the good work!

Hey mil3s, Nice job on this, it has a real feeling of form. The thing I noticed is that your shadow value is too dark. As a matter of fact, the image has too much contrast all around. The values are much more compressed than you have them. In other words, they are a lot closer to each other than you think. Remember this cast is made of white plaster, so the shadows wont be that dark. Also, there are areas where you missed some highlights at the edge of some of the forms pointing up to the light. Also, even the grooves carved into the cast have the same characteristics as other forms- core shadow-shadow-reflective light- and highlights. I did a quick paint over to show you some of things I'm talking about, I hope it helps :)

Wonderful job on the drawing. I also like the animated gif showing the differences. I don't think it's super important that your drawing is off a little bit. It doesn't have to be 100% accurate. What I think is most important, and you captured well, is the subtle values throughout the whole cast. Especially the reflected light. And even more important is your understanding of form. You've shaded the form in such a way that I can tell you understand how it moves through space. The depth is wonderful! All good stuff to say here. Move on to the next and Keep going!