Ok, so, here's the unpleasant truth: you DO need to keep practicing drawing, and you aren't going to see much progress for a little bit. I'd suggest you'd need to put in a solid half hour of practice a day, for at least a month, if you want to get good as fast as possible.
References are your friend - I have a practice regime that I do, to warm up when I'm about to work on something; four 2 minute sketches, then two 5 minute sketches, then one 10 minute sketch. I'll add some links as to where you can find good references of the human body in different poses (fair warning, most of these links contain photos of nude people)
https://www.posespace.com/posetool/default.aspx
https://www.human-anatomy-for-artist.com
as for drawing backgrounds, the same rules apply - practice, practice, practice! However, you can skip the hard bit by using google sketchup. you can build simple models using this program and use them as a base, and trace over them. Sketchup also has a 3d model warehouse, and you can download pre-made models. best thing is, the whole program is free!