I have some feedback. I am impressed by the improvement between the first and second pictures. And it shows that your understanding of light and color has improved. But don't think you're not good enough to post here. In my experience, everyone who is genuinely looking for help on this forum, gets it. The only exception being users that have reputations for asking for criticism and then arguing about it or not taking it to heart. Oh, and welcome!, if I even have the authority to say that. (I don't post frequently.)
You expressed your desire to improve, and to that I would say, what are your goals as an artist? If you would like at some point to create convincing, delicious eye-candy, then if you aren't already aware you should know that it is absolutely necessary to improve your fundamental skills. Are you as good as you would like to be at observational drawing? I know that when I first started pixel art, I didn't really consider the fact that pixels are merely a medium, and the same fundamentals as in traditional art are used. If you desire to improve, the fastest way hands down is learning to "see". Then you will be able to draw just about anything.