Would I be able to catch up next year?
I guess this is more of a question to answer yourself - you know yourself better than anyone else - but I'll try anyways.
Assuming it's only a few topics that you didn't quite understand, I would say that, given a moderate amount of effort, you should be able to properly review these topics over the summer break and be in great form for U3/4. Just make sure you're understanding the ideas behind formulae and practice problems, not just mindlessly cramming them. And of course, don't be afraid to ask for help 😃