It’s common to feel like nothing is sticking, no matter how many hours you put in. But, that feeling doesn’t mean it’s accurate. You know a whole lot more than you think you do.
If you feel like something isn’t working, switch to a different activity. Changing methods frequently is good for your brain. It helps with memory retention.
Make sure you stay active with your learning. Don’t just read and reread. Talk things out, write things out, do practice questions. Just keep moving forward.