I would love to help. You really put some effort into this and it shows, so nice job there.
I wanted to first touch on the anatomy since you were concerned. Fortunately even friends and moms with untrained "art eyes" can spot weird defects in anatomy and drawings because they have human pattern recognition brains just as good as yours. I can speak from experience, TRUST THEM. If the person who will never draw a neck in their life say's something is wrong it was their natural instinct. Don't convince yourself that its the perspective of this or that, just go backwards and see where it went wrong. And hold it against them forever!
But our friend is right. You painted a giraffe. (j/k) However your friend didn't do some googling to help you understand why. I have two words for you.
Also the ear is a bit high on the skull for the perspective on a head. See the drawing next to the constructed anatomy drawing.
The 'sterno' connects to the back of the skull behind and under the ear, then comes around the front to the collar bone as it travels down.
The trapezoids connects to the back of the neck and all the way out the shoulder blade, and just touching the collar bone. You don't have to show all that but just generalize and memorize the shapes here and where they attach.
I will say your facial construction and perspective was very good. Slight corrections only needed there.
But if you take the time to learn the shoulder blade and collar bone muscle groupings you will save yourself a lot of time. Its a very expressive part of the body, andcan make a character gender representation change with size.
Now lets talk about your picture overall.
How is it going to look on the cover of artstation? Lets try it out.
Well there you are, in all your glory, kind of hard to stick out in all that color though.
Lets adjust the color and brightness.
Thankfully we have photoshop.
now lets add some points of interest with saturation and color dodge layers, painting in some warm or cool colors eh?
Now how does it compare to the rest of the world?
Also with these adjustments there is so much more for the viewer to look at and be pleased by. I couldnt tell his eyes were bleeding before, cool!
It may not be what you intended, and it is a second opinion, and by far not finished. You must finish it on your own.
The work to be done with dappled forest lighting is simple. All the information is in the shadows, and therefore you can kind of blow out the dappled lit areas. Use the lasso tool to help you with this. It will also help to strengthen your composition, but if your not careful it can detract from your focus.
But now you have some better color and contrast to go and paint your edges with more finely. I hope this helped and can show you how you can adjust your images when you are in a tough spot.
Best of luck.