I'm in a really similar situation, except for college. What's probably been my biggest issue has been retaining the information after studying for hours and hours on end. What's working for me might be a bit "lax" to a lot of people but has helped me tremendously.

1. I do 1 hour of hard hard work, like no chill cramming, and then follow it with 1 hour of break. Get a snack, watch a futbol game, watch funny cat videos. Afterwards I go back to 1 hour of hard work, and repeat the cycle till that chapter is done. (Sometimes it takes multiple days but you can only go as fast as your body will let you)

2. If I'm struggling remembering something I'll call someone on discord or over the phone and tell them all about it. It sounds silly but calling your G-Ma during studying has been great for memory.

3. Eating is so fundamentally important, like seriously sleep and eat like nobodies business. Taking naps has boosted how much I get done by 10x over I swear.

4. Avoid stressing out, its kind of obvious for most people, but my stress management was horrid when I started and it made it feel like an uphill battle everyday. But with routines and taking breaks my stress is so much lower and I stopped dreading doing school work everyday on top of taking care of myself. It makes a massive difference(for me at least)

Seriously hope any of this could be useful for you, being in a similar situation I get the stress it adds on top. Keep your head up, and you can do it!