Build: Personally, I don't think the build is very good. I say this because there's nothing original about it, it's just your run-of-the-mill Minecraft pyramid and some floating islands. You need to try harder and pick out something that is unique, this just isn't gonna cut it.
Parkour: The parkour was both long and hard enough for the medium difficulty. Although, I recommend that you add more checkpoints as two is not very forgiving for this difficulty. Nevertheless, your parkour did have a bigger problem: variety. You used a lot of the same blocks/jumps for most of your parkour, proving to make it very unenjoyable to do. Don't be afraid to experiment with your parkour, incorporate more jumps to it! Also, you need to label your barriers (especially the ones in the interior portion of the pyramid with the lava) to avoid confusion.
I hope you take these criticisms into consideration when submitting maps in the future, good luck