I’d always recommend taking one aspect of mixing, search Google about it and work on it. I’m talking smallest chunks. Then work on the next. Some learned concepts will help with others so you’ll be faster in the next topic. Repeat. Then you’ll find there are different levels to mixing. What I mean by that is, you can first get your single sound sources to sound good, but in context they might not work together. That context is the next level.
The more you do it, the more you know how to achieve multiple levels at a time.
I think a big (maybe the biggest) part of mixing is training your ears. The question should always be “what is wrong with this xxxxxx”.