Drawing

Keep drawing and drawing, and always make sure to do the "skeleton" or "mannequin" thing before the drawing itself

Maybe as practice you could have the subject facing more to the side, and move the viewer closer. That way it'll be easier to notice if the features are really placed on a sphere, like if the eyes are different sizes. The hair has lots of potential depth, but perhaps a hat with flaps and a sawtooth pattern along the edge would be easier to apply perspective to and see if it's correct.

Try study doing the negative shapes to get the form right. One way to check or correct your own drawing you can just flip the drawing upside down or just flip it with a mirror. You will notice some drawing error like the eyes on the right side is small and etc. and lastly keep on drawing, I know that it will take a lot of time but one day your drawing from six months ago or a year will give you a big impression that you've developed a lot of your drawing.

For me it helped to draw sharp angles, using lots of triangles to describe the lower eyelid, nose and cheek.

Also looking at a reference photo with strong core shadows and drawing the black areas first/ generally drawing with pure black, pure white, no gradient.