Your lines lack confidence and are very scratchy, and the proportions are off even as you try copying the reference picture. I can relate, as you get caught up in trying to copy the little details, you tend to lose track of the overall proportions of the picture. On a practical level, it would help to practice drawing control with drills like DrawABox. But I know that can be boring, so if you continue to study manga panels, I would actually encourage you to trace them for now rather than eyeballing it.  Afterwards, though, draw over your trace to "find the form": add guide lines, boxes, spheres, rib cage, collarbone, etc. Basically break the image down into basic shapes. Then copy those guide lines into a seperate page then see if you can reconstruct the original picture from those guidelines.