Build: Personally, I don't think the build is very good. For starters, it's just very unoriginal. It looks like the countless other nether fortress maps we've seen submitted. It doesn't take a new and exciting take on the theme. And, it's not very well-executed either. You have a bunch of messy floating parkour and a plain/empty nether brick cylinder.
Parkour: The parkour fits the hard difficulty length and difficulty wise. But, it was not very entertaining to do due to the repetitive nature of it. There were just too many fence and ladder jumps, it felt like I was doing the same thing over and over again. Don't be afraid to experiment, try to use a bunch of different blocks/jumps in your parkour to make it as fun as possible.
I hope you take these criticisms into consideration when submitting maps in the future, good luck