Review c:
Theme
Not the best theme, there is already some "Crystal" theme map (Crystalized ( and GlassMuseum ?)) and it's a pretty hard theme.
Be careful next time !
Build
Looks good but can be better, try to not build flat platform but try to make it like a floating island.
Also, try to have a main build and not several little build on your parkour, so that you can put your parkour on/in your build and not scattered.
Last thing, try to have a build who fit more with the theme ; I don't really know why you put a waterfall on it.
Parkour
Not really good, there is not a lot of variation of blocks, try to put some slime, soul sand, more ladder... through your map to avoid repetitiveness.
Also, please avoid using invisible block, or just try to put some sign on it to warn player : without sign on invisible block, your parkour is a bit confusing.
An other thing, your parkour is a bit easy for a medium map, because your map is a bit short and don't really have some hard part, the only thing who up a bit the difficulty is there is not a lot of checkpoints.
Miscellaneous
You need to put a yellow wool (Because medium difficulty) below the pressure plate at the end of your parkour and put it one block in the ground to avoid glitch
My opinion
Not gonna be accepted, the theme is too hard so it's really hard to build something decent with it. Also, your parkour need to be improve.