>>14283453First, you can't just watch a video and expect to instantly know and be able to apply the concept. You have to practice by drilling example problems over and over. That's the only way. Shit takes time even for the best of us.
Second, just buy a book and go through it sequentially. Literally any textbook printed after 1990 for calc or below will be exactly the same. Just find the cheapest $3 text on amazon. Keep it on your desk, study for an hour a day, do all the problems until your comfortable enough to move on.
The sequence goes Algebra/Trig or "College Algebra" -> Pre-Calc -> Calc (any standard calc book goes from 1-3, single to multivar).
After that you should become familiar with mathematics proper. Different people have different names for what a course like this is called, discrete math, intro to analysis, intro to proofs. Basically you want to learn logical statements, techniques of proof, basic set theory, basic number theory, functions, relations, and equivalence relations/classes.
Once that's done you should read a good linear algebra book, I prefer Roman, others like Strang. Its important that you understand both the applications of linear algebra and the conceptual theory. This is why its important to know the all the proper math stuff before taking linear algebra. You can plug and chug matrices to get a result but you wont understand the implications of what you're doing without understanding the abstract conceptual components.
Then the door is wide open, study whatever interests you. Diffeq (ordinary then partial), abstract algebra, analysis, topology, stats/probability theory, advance linear algebra, complex analysis etc.
Some will say learning proofs is not necessary for linear algebra, and a full course on linear algebra isn't required for studying diffeq. I think without that your understanding of diffeq will be superficial at best.
