This is coming along nicely. Well done for persevering.
I think the hair looks very soft and while that does work well to express the texture I still think that it's worthwhile to tighten up a few of the strands to pick out some detail with some subtle highlights. Also by choosing a dark colour it does make it more difficult to show form within that value range. Introducing a paler midtone at the top of the head could improve it a little more but I do like the little sheen of light at the front.
The main advice is still to be patient with your brushwork and choices. I know that does sound very boring when you're eager to work quick and finish something, but that speed will come later. For now you just need to build the habit of working precisely within the linework to control your edges and find the forms with shading.
EDIT: And I've just realised that you posted the pic while I was typing this. I must learn to type faster.
But my advice here still stands.