The only awful thing about the shading is how low the contrast is in confront to the main red color of the dragon. Only thing I could distinguish before opening the picture was the eye, since it has such a dark and well-defined outline/form from the rest.
Raise the contrast between light and dark, between the main red and the shadows, and it'll turn into a wonderful sketch!
About the rest of the pic, as Paladin Danse would say: "Outstanding."
One of the few scalies that actualy makes you shout "Scalie!" when you see it, and the texture used for its skin/scales greatly helps the effect.

I tried some things and changed some colors, it is already better now, thanks for the help :)
Have to learn a lot about colours.

Hehe, you're not the only one. I need.to learn a looot about colors myself!
You're doing well, keep going!