>>16873285
If you pick up the textbooks used in classes and actually go through each chapter and do half the exercises you will get more education than the classes themselves.
On the issue of time efficiency you can use your own judgement for if the exercises are too easy and need to be skipped--that is, you know you will get them right.

>>16873292
I've used digital textbooks that are used in my country in schools but I've seen they're quite flawed with wrong answers from the book itself. Also, they're littered with colour, like a unicorn threw up on them, it distracts me. Right now I'm using commie era "golden age" textbooks and I feel like they're more thorough and answers are more rigurously checked since then they had to make them by hand.

After you have solved a problem, look at the official solution and compare.

theres no substitute to a ruthless professor and competition with peers.

>>16873285
Khan Academy is good for self assessment. KA has interactive exercises that offer immediate, specific feedback. There's no problem if you skip their videos and use your textbooks. You will learn to use textbooks better if KA exercises force you to do so

The vast majority of my professors suck and so do their lectures. I've learned almost everything on my own from textbooks. I should agree with

>>16873315

At an early stage I grew lazy because I didn't feel challenged. When I went to study for one semester in a bigger university as a exchange student, I find myself really motivated and productive after encountering with many other people who were seriously committed in their education and I could compete with (in a healthy way, of course).

Later, I could get a good source of feedback and support from math communities (those which are willing to help you and are not a mere circlejerk). You could find those communities on Discord, Reddit and Telegram. I encourage you to look for them.

Thank you everyone for you feedback, you're very nice. <3