Your sketches on paper are too dark and you’re pressing too hard on the paper. I recommend drawing lightly with a 2H pencil so you can easily erase the lines without leaving a mark.
The justsketchme thing is not a rough/sketch layer, It’s an anatomy and pose reference. You need to do another layer in between those two. The sketch layer is where you make all of your mistakes and then correct them, You don’t need to add every detail, nor does every line have to be perfect, You just need enough information to guide your final line.
For example:
Sketch:

Lineart:

Please note that in the example, the sketch was done over a screenshot of a 3d model. It is also a little bit cleaner than usual due to some quirk of the production methods.
Edit: Forgot to include the original sketch, to avoid making you think that “real” artist can draw something like as a first step.
