How can i improve my art skills?

Nice start/progress for 88 days!
What most ateliers teach is to segment/divide an object.
Example:

From there, you practice values (level of darkness from 0-100). Also understanding form can greatly help in understanding how shadow and light interact on the object!
PS: Good thing you understand that shadows aren't all black, but just a darker value/chroma than the lit surface! Keep it up.

I can't offer any kind of specific detailed critique, however will share a video that speaks more in-depth of what you may be looking for :

As cliche as it sounds: Keep practicing. Even when you don't want to hold a pencil/stylus/whatever.

Eventually things will start coming a lot more naturally to you. Also, your muscle memory will be built, sort of like playing an instrument. Good work. Love the colors.

When making graphical art, there is a helpful process that I call the three step process. Which is to make a line art. Then to make the line art into a black and white grey-scale, then to finally add color. As for your painting, it's pretty good however some proportions of the face are a bit off. The derp eyes and ears are probably the biggest issue.