How do I make a working knife, with randomized damage and durability?

I want to know how to make a knife. No not the models, but a working script, that has damage randomized between 15-20 damage, and the knife to have durability. Specifically, have the knife be removed from your inventory after killing 10 people. And, I want to know how to sync my animations. My animation name is "attack", and the animation ID is 6398856018. I have 2 scripts, "Attack", and "Damage". I also have a BoolValue called "canDamage". And my scripts are (in order from the Attack script and Damage script)

local gear = script.Parent local attackAnim = script.attack

local cooldown = false

gear.Activated:Connect(function()

local humanoid = gear.Parent.FindFirstChildWhichIsA('Humanoid')
if cooldown == false then
	
	cooldown = true
	
	local loadedAnim = humanoid:LoadAnimation (attackAnim)
	
	loadedAnim:Play ()
	
	local canDamage = script.Parent.canDamage
	
	canDamage.Value = true
	
	wait (0.16)
	
	loadedAnim:Stop ()
	
	canDamage.Value = false
	
	cooldown = false
	
	end

end)

2nd script (Damage)

local gear = script.Parent local hitbox = script.Parent.Hitbox

local canDamage = script.Parent.canDamage

hitbox.Touched:Connect(function(hit)

if	canDamage.Value == true then
	hum:TakeDamage (15)
	
	canDamage.Value = false
end

end)

I also have a part on the knife part called "hitbox", and it is the hitbox.

someone please tell me what I did wrong, and tell me how I can randomize the damage between 15-20!