Hello KevinPlayz312,
Unfortunately, I will be
Rejecting your map.
The theme isn't original, as there are many maps with minecraft/biome themes. Please refer to the document in this thread -
https://manacube.com/threads/parkour-list-with-theme.20194/ to make sure your map idea is original.
There isn't really a main build. In the future, try to have one or two larger builds that represent your theme, then build the parkour into that, rather than having a lot of parkour floating over the void & islands.
The parkour has some variety which is good, but it does feel a bit repetitive at times. Try to experiment with a larger variety of blocks and items when building parkour, as well as the way you utilize these, as this will make your map more fun to complete.
The difficulty is good for an easy/medium map, and the length is good for a hard map.
Thanks for submitting your map! I hope to see more maps from you in the future.