If you have the time maybe look towards a community college and take a modern mechanics class! I took one in undergrad and it gives you insight into special relativity and basic quantum. Though I don’t remember a lot of it, it was really exciting to be able to practice the math and be able to ask the professor my questions.

I feel like with these topics you need to dive into the details to gain a strong understanding but then you only realize how much there is to learn.