>>4392090It can take hours, even for professionals who know what to do without the guesswork needed.
To start off with you need at least two layers (lines on one layer, colors on another). Then if you're confident you merge the two layers together and shade on one layer, or if you're not confident you make a third layer on top of the two previous layers and go over the drawing that way.
The drawing in this post is better, there are colors in the lines. However you didn't finish filling in the top part of the picture unless that's meant to be white. The color choices aren't great but at least it's something.
