How do you make a delay between doing damage?

Simply add something called a debounce, here's an tutorial on it: https://www.youtube.com/watch?v=HoZkuvd6RPA

Just use a wait statement...

wait(2)

How many seconds you want it to wait in between.

just add a debounce, like one of the replies mentioned. debounces are for a block of code not to run in a certain amount of time. in your case you could do something like this:

debounce = false -- first we create a variable called debounce and set it to false

function damage()
    if not debounce then -- the code inside this block will only be executed if there's no cooldown (debounce is set to fall)
        debounce = true -- sets debounce to true
        -- do all the stuff you want here
        wait(1) -- cooldown
        debounce = false -- sets debounce to false
    end
end

feel free to clear any doubt about this