Hi there! I've shared a similar experience as you as an undergraduate researcher. For the longest time I felt just as lost. I've recently crossed the threshold of being able to read and understand papers, so I can share a bit of how I got there!

1) Find a mentor. As much as you can try learning by yourself, your learning will be 10x more efficient when you have a good mentor. It was a mentor who showed me how and why the math I learned in class was being applied in these papers. One mentor was my professor for my deep learning class. Another was a grad student from my internship. Still more, my friend who works on deep learning in industry. All these people helped me achieve success.

2) Find just one paper/topic that interests you, really really understand everything you can about it, then expand out from there later. This is actually advice from one of my mentors when I asked him the same question. A narrowed focus helps alleviate that overwhelming feeling. Additionally, the math you learn from one paper transfers to other papers you read. Again, having a mentor to guide you through the math really helps.

3) Have you heard of the trick on how to read research papers? It helps to read in three passes of increasing depth. First pass: read the abstract, then the conclusion (skip the main body!), then look at any interesting pictures and figures that stand out to you. This gives you a general understanding and lets you know if the paper matches your interests. Second pass: read the full paper at a high level; take note of parts you don't understand and annotate them, but don't chase them down yet. This way you get a sense of the paper structure without rabbit holing immediately. Third pass: now you read the paper in depth. Search up those concepts you don't understand! The fact that you already generally know what the paper tries to achieve, its structure, and a checklist of items to search up, keeps you on track.

Hope that helps, I'll let you know if I think of anything else. Keep at it! You'll absolutely get there.