Don’t worry you have good start already.
First try to work a little bit more on lower levels with move brush (no need to go so high, before you add wrinkles).
Try to refine his neck behind his head, so it wouldn’t stick out so much. Search for skull references so you can compare where the neck ends and where the skull starts (somewhere behind middle of ears).
In past i used some Xray photos so I could see flesh and bones (might help you too).
You will probably get in trouble with that topology on his nose, you might leave it as is but probably there will be some bad pinching on nostril.
Try to tweak lips more, corners of lips should be more defined (open mouth is hard for beginners, I know that from experience)
Take small steps, one by one, don’t go into details before nailing basic shape.