Tried looking for a reference as similar as the one you chose, when doing portraits it's important to break down everything into simple shapes, then adding details after, this way you can keep volume and proportions as accurate as you can, then add detail on top of that after, especially with how hair flows and getting the neck area more correct. This will help making the drawing feel more realistic & just having more depth. I can now easily add more and more detail and fine tune my drawing to get it closer and closer to my reference, but i kept everything relatively simple! Especially with hair it flows from the roots and gravity pulls the hair down so it flows with the head naturally, just keeping this in mind should help you understand hair a bit better as well. I highly recommend going through the "intro to portraits" road on ArtWod this will address the direct problems that you might be encountering! Happy Drawing!
