For advice is learn about the head bone.
This will help you more about drawing
Thank You, Ishigami614. If i understand your comment correctly, you are referring to that fold underneath the ear that looks like the sternoclidomastoid. If you see the picture reference that was being used, that fold you see is simply skinfold as the model's head wäs photographed from the rear and his head was turned sharp to the right. But to your comment, it isn't rendered correctly as i have a tendancy to rush the drawings because of the time restraints. I will try to improve in the future.
Hey there! Love the spunk that comes out in this drawing of yours! The only thing i have to say about this drawing is that the proportions stick out to me a lot. I can tell that rather than using shapes to draw this head, you drew it using the outlining, or contours, of the head. The only issue with this approach is that proportions can get messed up, and the drawing flattens out. Instead of using those 10 minutes to rush the drawing so you can have time for shading, I'd suggest using that time to identify the shapes of the head, the proportions (where each facial feature is placed in relation to other facial features), the angles of those facial features, etc.
Thank You, Emmamora. I had not recognized that the proportions were off. That is useful advice. I will strive to improve for the furure.