I am loving this YouTube video about learning music theory. I got a midi keyboard for my 2019 challenge and have realised that there is a lot to learn to get to the point of making something good.
Petapixel feature a simplified guide to getting started in Photoshop which was developed by photographer Devon Mikale.
Lots of graphics that illustrate many of the most commonly used options. There is also a downloadable pdf available on the site.
Wish I had something like this 15 years ago!