Only a few details were added since yesterday because they took a little longer than expected. - Nevertheless I am still making a noticeable progress. I was able to improve the shading process, which consists of the shapes contour and face. To achieve a fluent passage, you have to remember both of it sometimes, what was the reason for some struggling today. By the way, Illustrator provides a bundle of different patterns you can use for different types of surfaces. I already used one of these presets for the grass, and I will probably use some more of them for the waters, the trees and the streets surface tomorrow. Of course it is possible to create your own pattern, that can be saved and selected again afterwards. But first I had to figure out how to even use these presets correctly regarding the scale, the color and the background.
Some of the shapes already got their basic color, but these colors might change again tomorrow. Everything shall be well-matched, so the illustration can give a self-consistent impression in the end result. To achieve that, there is still some work to do.