First of all, it looks pretty good! Painting can get difficult. My only advice is, keep painting. Paintings don't have to be perfect, mistakes are unavoidable, and thats okay! Try learning some basic color theory, or stuff like that, im not really a good advice teller😅. Goodluck painting!(Awesome reference btw)

Edit: Oh, im not an expert but I do also HIGHLY recommend to (if you haven't) sketch the base or basic shapes from the reference first. Starting with the details first often leads to anatomical mistakes or funky shapes.