There is so much completion in your work. Take a look at this: https://skripthub.net/tutorials/75
This tutorial will help you create a proper cooldown

And due to the performance and the fact that no one else is using Skellete bossbar other than you, I recommend you use SkBee bossbar instead of Skellete bossbar.
https://github.com/ShaneBeee/SkBee/wiki/Bossbars