Hey Rubenderidder,
I'm here to give my personal opinion on your map. I am no map judge so my opinion means nothing in the final decision if your map gets rejected or not.
THEME
Your theme is unfortunately unoriginal as we have many maps with this theme already [RainbowRoad, RainbowCone, Rainbows and many more]. In the future, I suggest you look through the map document and look for a theme that isn't taken already.
BUILD
Your build is also a main concern as it's just a floating build with no scenery or "main build". Adding more to a build would make your map have better chances of getting accepted. E.g: Stars, clouds, a sun etc.
PARKOUR
The parkour is also a big issue. Because of the very much repetitiveness in the build your parkour gets affected as well by it. It's boring and makes the map uninteresting to play. Another big factor is that your parkour is floating, which isn't accepted anymore on parkour. Try use diffrent blocks and entities when making parkour such as: minecarts, trapdoors, doors, pistons, chests, water, etc.
Good luck though! :)
-Nathan