Welcome here !

Don't underestimate yourself too much, being here and spending time reading the Sequences at your age is already something great :) And if you don't understand something, there is no shame to that, don't hesitate to ask questions on the points that aren't clear to you, people here will be glad to help you !

As for quantum physics, I hope you'll love Eliezer's QM Sequence, it's by far the clearest introduction to QM I ever saw, and doesn't require too much maths.