>>7785256 (OP)
You want to learn how to draw a specific thing in a short time period. This is one of the few areas of art where there's a clear path to your goal: copying. You don't need to worry about the fundamentals right now. Begin studying copying techniques. Amass a sizeable library of references, and copy them as accurately as possible.
When copying, an important skill is knowing how to draw from the outside in. By that, I mean mentally (or physically, if you prefer to study that way) breaking down your references into huge shapes. Block those out on your own paper, and then break those shapes into smaller shapes, progressively getting more detailed. Do not try to draw in parts, finishing the head and then the arms and then the legs and so on. Draw in wholes: a whole general body (which can be nothing more than 5 lines roughly outlining the silhouette), a whole better-detailed body, etc.
Learn how to gauge measurements and also how to measure elements against each other. For example, if the head you drew looks right but the arm looks too long, look at how long your reference's arm is compared to its head and adjust the arm you drew accordingly.
Copying is fortunately one of those things that requires very little creativity. That doesn't make it any less tedious, but it does mean you can just brainlessly hammer away at exercises like you'd study for an exam without really understanding what you're doing.
