I think your on a good way, you have to do the hair in multiple plan, by the more lighter to the darker.
Try to make the darker hair stand out on your shape I don't know how to say it I'm sorry.
At the end you make the lighter hair flash by a contrast white if you will, it will be more attractive to the eye and also more realistic ;)
Good job on keeping overall shape of hair and texture. I feel like (especialy in the last drawing) you focus a bit too early on details. Try dividing hair into few big shapes and then dividing those shapes into smaller shapes. Hair tends to clupm together. I already can tell you're trying to represnt reflection but keep in mind which part of hair is in the light and which is the shadow. On drawing nr7 entire left side is brighter than the left but on your drawing only highlits are visible. If you have hard time noticing those big shapes of value try squinting your eyes or getting further away from your screen. Light is just like gesture, you start wirh bigger forms and ten go to detail. You can try making some quick sketches witch just determinig lights and shadows without drawing each individual hair