I find 3blue1brown to be a great resource to build up good intuition about math topics, his videos about calculus and linear algebra are wonderful in particular. https://www.youtube.com/playlist?list=PLZHQObOWTQDMsr9K-rj53... is his essence of calculus series, I found the visualizations made it a lot easier to grok.

I can second 3blue1brown as intro, but anything practical needs practise. Get your local 12th grade or undergrad math book which has problems to solve will bring more focus and faster learning. Have a list of problems to solve in your head while learning theory has been faster for me than just learning theory.