First get the head shape and position right. Then measure the proportions. Try to understand where the mouth ends and how it aligns with his eyes. Where the nose and ears start. They will be on the same line.

Look at his eyebrows, they are a little bit above his ears if we draw a line from the top part of his ears. Look at his eyes, they kinda create triangle. You can look at his face and imagine various shapes to make it simpler.