I like that the skyline has an area of tall buildings, this gives a focal point. The wanderer and tree in the foreground also balances the aforementioned focal point. Some points to improve:
- You use 1038 colors, that is way too much! I think you only need around 16 color.
- The overall cityscape looks flat (in the 3rd dimension), like paper cutouts. The most distant buildings have the most '3D' going on (showing (parts of) their sides), even though this perspective would be most pronounced in the frontmost buildings. The foreground buildings look too small, and you should be able to see their roofs if they are below the horizon. You should not be able to see the roofs of the highest buildings, because they are above the horizon. I do recommend moving the horizon up or down (probably up), so that it is not centered vertically. Learning to draw realistic perspective is really important!
- I think that the sky would look better if the sun was place closer to the horizon. The sky 'burn' looks better as an upward gradient.
- The lights in the buildings are too evenly spread. I quess you randomly placed them, however the human mind is bad at generating random: It is biased towards eveness in distribution. Why do the buildings closer to our viewpoint have (relatively) more lights on? This actually bad for the sense of depth: Lighter areas appear further away. (You did use this effect correctly in the base color of the buildings though 
).
- The distant row of hills are too regular.
- Elements of the foreground and its highlights are especially sloppy. The overall shapes and lines are really jaggy and look unfinished. Some transitions from light to dark are too sharp and need AA, but you need to master the basics first.
- One hill has highlights on both sides?
- The shadow of the wanderer needs to be way longer (the lower the sun, the longer the shadow) and more skewed to the right side.
- The tree shape looks off. Use reference images!
I like your spirit, keep practicing ! The most important advice I can give you is to work on much smaller pieces.
Hello Taertage,
Thanks a lot, I appreciate every tip,
thanks for check my work!