This isnt an end all be all but can be a very good place to start. lol giving this guy free advertising.
https://www.youtube.com/c/learntotune/videos
He has good tuning basics and theory videos but you have to search for them because there is no playlist.
You show the paid version of it which is very in depth. If you want to have the understandings on what things change and test around yourself then he posts lots of free videos on his youtube channel.