How bad are Calc unit 3 and 4?

I really did NOT do well in unit 1 and 2 (70 unit one and im expecting 75 ish unit 2). How do I do better? I think we'll be done calc and a test or quiz for vectors before midterm and i really want to do better. The goal is literally just 85 I dont want anything too aspirational because I know my electives will help.