I say this a lot, and I'm going to keep saying it: The best way to get better at drawing comics is to draw comics. Not by redrawing your old pages out reworking your old scripts, but by going forward and doing new things and drawing new pages, learning from any mistakes or hurdles you encounter in the process, and then applying that to your new pages going forward.
Nobody expects someone's first comic to be amazing - it's a brand new skill that you are learning and figuring out as you go. But you will only learn it by doing it. The more pages you draw, the more you'll figure out what works and what doesn't, and you'll naturally get better at it by virtue of continuing to create.
Even people I know who went to college to learn how to draw comics agree that they still learned so much more about drawing comics in the several years immediately following college, when they were working on comic series or webcomics and actually drawing new pages on a consistent and regular basis.
There's also always going to be an infuriating learning curve moment where your knowledge exceeds your skills. You will be able to look at your art or your pages and know that it's not right, and probably even know why it's not right, but lack the practical skills to elevate your art to that level. When that happens, you just need to push through it and force yourself to draw consistently, study other artists, learn new techniques, and build your skills up.
For just the fundamentals, to get you started on understanding the theories and logics of comic pages, just... Read up on it! There are a ton of tutorials online that will help you with your shot calls and page layouts. Read books by Will Eisner and Scott McCloud about making comics. Absorb as much knowledge as you can, then do your best to implement it. And when a page doesn't work out quite right, don't keep fiddling with it and redoing it and redrawing it! Move on to the next page, and try to figure out why your previous one didn't work, and then consciously do something different with the next page.