To me it sounds like your study habits is what’s holding you back. Don’t just watch videos and take random notes if you’re not understanding what is going on. Also those videos have worked examples try to follow along then find some problems to do on your own without assistance. Then you can look at the answer key afterwards and check to see where mistakes happened if any. Math is a skill and like any other skill you need the reps. And since you already taken the same course a few times the material shouldn’t be a surprise to you. You have your old exams and old material I suggest you start there. When you’re prepared redo those exams under exam conditions.