How to go about making fast communications?

Hi. I am currently making an ability system for my game. However, I ran into a problem with speed. Roblox’s server and client takes ages to communicate. If I want to make cooldown server-side, the client side won’t show it on the GUI fast enough. If I make it client-side, it’s far too easy for hackers to fire the same events. I also tried using both, but they quickly become desynced. How would I solve this issue?(by the way, all animations, damage handling, ect are all server-side)

I appeared to have solved the problem. Turns out there was a problem with my script and the communications aren’t actually that slow.