>>7681358
it's all form bro, shapes and all that. Rather than spending an hour trudging through trying to get a bad sketch to look good, take a step back to observe and think. Try to get things down with as few of lines as possible.
If you notice something small missing go ahead fix them, but if the drawing feels too wrong and you don't know where to begin on fixing it, just go ahead and start a new sketch and keep the old one somewhere.
>>7681361
You can play with shading all you want, but don't do it out of obligation. The only thing you should ever do out of obligation is sit down and draw. When you study shading simple things with clear planes, they don't look too bad. Though I really wouldn't worry about shading the girls you don't understand the form of just yet. Most importantly, draw what you're inspired to and use your brain while drawing always.