It might help to make some very light marks in the beginning to indicate key landmarks. Think big to small. Once you have the big structures in place, then you can move on to refining and simplifying your lines to CSI. It could also help to try to slow yourself down while drawing. Try to be very intentional with each line. It might slow you down more than you'd like but you can build speed again by practicing this way consistently. The snail looks great! You got some really good stuff here, hope this helps!

please try sketching first. This is a good attempt but you need to work out the problems in charcoal first.

in the final photo I can see that your halftone is too dark in many places, like between brow.The middle shot is actually better

your first photo shows how you did a good job of separating light from shadow with two obvious patterns. You kind of lost some of that separation with too much lightening of the shadows. but overall it's a good effort.