It's awesome
I Lol'ed when I saw red hair.
You made me giggle.
Natural hair...muzukashikunai yo, jappy-chan.
The key is on 'burn' tool and 'dogde' tool. For the lines on hair, please keep in mind that the size of the 'burn' and 'dodge' tools must be small. As for the shading, use the burn tool to darken em. Last, the lighting. You need to imagine where the lights came from and...made em shiny.
Some little tips : I suggest you not to draw lines (Black lines when drawing sketch) on hair.
Make them blank, draw the lines on next layer!
That's all I can tell you for now. I'm not really good at teaching but perhaps someday I will post a simple thread of how to color hair and lighting.
Oh and... actually, I think you have a great potential jappy. When I'm at your age, I can't even do any coloring! Lol