There are a couple of things preventing me right now. I need some advice and help from you guys :)

1. Currently I am having a hard time concentrate and gain motivation to do anything. Is this depression? I don't know. ADHD? I don't think so, as I have never had any of these problems before the lockdowns.
-> Any legal supplements or things I can do to fix this. I'm not in the mood to get on Adderal or SSRI's. I eat a pretty healthy diet, and have been losing weight. Concentration is a big issue I have, but if I'm interested in the subject, I can focus on it for HOURS.

2. I need to get better at math. All my life I have been shit at math, and have never gotten better. I really want to learn how to understand complex physics, algebra, calculus, etc. I understand a lot of other fields, and this field is the only thing I lack understanding of.

3. I want to learn the details of things. I want to know the exact properties and things that occur in cells. I want to understand complex theories of the universe, etc. Not elementary shit.

What should I do? How should I go about this? I have tons of extra time right now and I want to get smarter.