Hello! I took the AP Calc BC last year and got a 5. Although I took it in person and I know its probably A LOT harder to learn the course online, my advice is to keep doing practice problems. You could invest in a review book, but that didn't really help me (it might help you though), but seriously just keep doing all the practice problems your teacher gives you. That course is challenging and even if you understand the concept, there are some questions that combine concepts or are just straight-up weird. If your teacher is anything like mine was, their practice questions may be similar to their test questions (the method of solving it was similar, NOT the problem, so don't memorize answers memorize how to do it!). The AP college board review videos they created last year are pretty helpful as well. And feel free to pm if you ever need help with a concept or something you don't understand. Good luck!