>>7633746
You are at such an early stage that there's no point in giving advice for a specific thing like portraiture, instead you should try and improve your skill overall. I'd say pick up a beginner course like Dynamic Sketching and stick with it for a while.

If I had to give specific advice, however, I'd say focus on learning the planes of the face (Asaro head) and the shape of the skull, and then practice separating the different value groups of the reference. Once you have all that down, you should be able to combine that knowledge into a semi decent portrait. Getting the likeness down comes with practice, I haven't really cracked this one myself