Try something like Khan Academy and some YouTube lessons

start with “functions”, refresh yourself on polynomials, skip trig to start with, and then look for calculus and derivatives.

Functions are the foundation of modelling change, then calculus is the tip of the iceberg. When you understand derivatives, the next course would be anti-derivatives and integration. For calculating integrals just focus on the concept, there’s a whole world of methods to calculate them that’s less important than understanding the idea. 

It’s a good idea to do lots of excercises on paper and most frontier AI will be able to make you problem sets and evaluate your work.