How to learn Linear Algebra ?
My recommendation is that stop following all the random material. It rather confuses you. If you get stumped by things like “Eigen Vector”, “Singular Values”, you have landed at the correct page.
Best way, I feel is to spend a couple of weeks and thoroughly follow the lectures from MIT OCW by Prof. Gilbert Strang (MIT 18.06). After doing this course you should hope to not be scared anymore with Eigen Vectors anymore. If you are wanting to get into research and build strong mathematical foundation, a good grip on linear algebra is a must. Also for learning convex optimization, this course is a must.