The folds/ wrinkles on the head all have the same c-curve design. It looks repetitive, I'd say design each wrinkle and fold differently. Look at Stan's drawing, no two wrinkles look the same, he designed each one to be distinct. Here's a video by Court Jones: https://www.youtube.com/watch?v=DaY_KpFpHrk. I think it would help you design your shapes a lot better. Marco Bucci also has a great video on shape design: https://www.youtube.com/watch?v=-ZknWKTpc90. Otherwise, good job.

Sweet you are getting there. Just review the structure lesson. This will help you a lot. For example Reiner the head mass is a sphere with the side chopped off. Keep going

Wow! I think it looks great man. You've captured a real twinkle in the eyes and had a real go at the rendering. The original reference's face is a bit shorter and wider than this. Take Stan's tip and boot up a digital drawing software like photoshop. Then, superimpose the original reference on top of this photo in a separate layer and line it up as best you can. Then turn the reference on and off and play a game of spot the difference. It's a useful exercise in training the artist's eye. Then, if you're feeling driven, try to do quick redraw based on what differences you picked and focus purely on the proportions. Don't worry too much about shading on the second go. You've already proven you've got the skills and now proportions is what needs a bit of love. Best of luck!