My fall damage script keeps giving me several different errors?

I'm attempting to make a fall damage script for my game, however when I try to calculate the amount of time the player has been falling it prints 'nil'

I tried to use a while loop and a repeat loop but both printed the same error: Workspace.Louscascicly.FallDamageScript:30: attempt to perform arithmetic (mul) on nil and number

Here is my script:

local PlayerService = game:GetService("Players")
local Player = PlayerService.LocalPlayer
local Character = Player.Character
local Humanoid = Character:WaitForChild("Humanoid")

local FreefallTime

local DAMAGE_PER_SECOND = 5
local FATAL_SECONDS = 15
local MINIMUM_SECONDS = 3

Humanoid.StateChanged:Connect(function(state)
	if state == Enum.HumanoidStateType.Freefall then
		repeat
			FreefallTime = FreefallTime + 1
			print(FreefallTime)
		until
			state == Enum.HumanoidStateType.Landed
		
	elseif state == Enum.HumanoidStateType.Landed then
		print("Landed")
		print(FreefallTime)
		if FreefallTime > MINIMUM_SECONDS then
			if FreefallTime > FATAL_SECONDS then
				Humanoid:TakeDamage(1000000000000)
			else
				local RefinedDamage = FreefallTime * DPS
				Humanoid:TakeDamage(RefinedDamage)
			end
		end
	end
end)