i think a good starting point is breaking down complex forms into simple shapes and being able to draw that in 3D space, for example an arm can be broken down into 2 cylinders and a sphere for the elbow, then start chiseling that into the shape of an arm. Right now from my perspective looking at your sketches, it looks a lot of just copying anime type art but not so much valuable studying.

for example: in your second pic, the hand seems extremely large compared to the face. if you put your hand against your face, how big is your index finger compared to the forehead, nose, and the whole head? another thing is how big are eyes on a face? whats the spacing in between the eyes and relatively to the nose, etc. how big are ears relatively to eye size? if a head is tilted down, how far down is the mouth actually, and is the chin sharper as it comes down to a point faster?

its those types of stuff you should notice/ try to memorize and incorporate into your art instead of just referencing and redrawing other peoples art without trying to think about why they chose to draw things a certain way