You’ve picked a great subject / reference material — it has some basic shapes, understandable shadows, which are great to start self learning.
Important thing you can do is save your work and do it again in a month or three to examine your own progress.
Another sub-exercise idea, after you will finish this version, try to come up with a totally different color scheme, not present in the reference image — this can help a lot because you will force your own creativity to kick in, instead of just making a copy of something, plus good coloring is deceivingly hard to pull off..
Some advice (and take it with a grain of salt I’m no artist) but for some reason the bottom lip of the visor that’s shaded is throwing me off and idk why