SEO can be learned with many ways like training in a company , course on Udemy , YouTube and when you have learned the basics of SEO , practicing is very important , read articles related to SEO, keep updating yourself with Google updates and lot more.....
I recommend learning the fundamentals of SEO testing. There's a community called internetmarketing.gold created by Kyle Roof and Ted Kubaitis and they are phenomenal. They're brilliant, open to answering any of your questions, and they teach you how to test and verify the things you hear about the google algorithm.
(Disclaimer: I started a community member and was so inspired that I actually ended up working with them so I am admittedly biased.)