Another note here, since other posters have already provided with a plethora of resources.
There is no escape from learning maths by picking up some pens and paper (or their digital equivalent) and just doing it. Learning maths is like learning how to ride a bike - you don't simply watch videos or read books to learn how to ride a bike, you ride a bike (and fall a million times) to learn how to ride a bike. Understanding comes with countless practice. I assume you know this already, but I think it's not a bad idea to further highlight the importance of having a go at attempting problems, even if you don't understand the topic at all - just like the first day at a new job.
If get stuck, I'd say (i) reviewing relevant materials (textbook/Google/YouTube is good, ChatGPT is dubious but good enough if you actually check its answer), usually there are worked examples there; and (ii) discussing with someone (be it his instructor, his peers, or here in TSR) about the problem would be best.