please do not despair. I can understand your problems well, but they can not be solved at once. We say here in Europe "Rome was not built in a day" :-)
It's the same with painting. Everything needs time and practise. I am prof. Juggler/Sircusartist and we talk about "hours and hours of frustration" but we do not capitulate :-)
At first, it does not matter if you're digital or traditional. The crucial things are a certain know-how how to approach a picture.
You are already on the right path. You work from rough to fine. At the beginning is a good and strong drawing, then details are far from important, you block the basic colors.
Soon there will be an important work, which comes far before the details, light and shadow. This is determined roughly by light and dark tones, and
how the figures become more plastic and three-dimensional.
It does not matter so much whether you make the background at the beginning or the end.
Digital you can work mostly as in Photoshop with "layers".
Do not be overly distracted by technical issues like program details.
The goal is to "paint"!
If you want to see how I act, I have on my website too
in the digital works, the "WIPs" with set. It's not about being a poaster, it's about showing you how a way can be, it's my way, it's close to
"normal" way off and you can see something the individual steps.
Look here (hope, that is allowed to post the link).
A good teacher online is Aaron Blaise. He was Artdirector at Disney and he knows very well to draw and paint digital and traditional. On his youtub Chanel you can find tons of tutorials!