Why my Humanoid.WalkSpeed won't change?

I have this problem. I can't change it with codes! He doesn't send me any error too. These is my code.

local Player = game.Players.LocalPlayer
local Character = Player.Character.Humanoid
local WalkSpeed = Character.WalkSpeed
local ControlHolding = false
local MoveHolding = false

local Animation = Instance.new("Animation")
Animation.AnimationId = "http://www.roblox.com/asset/?id=1909808255"
local Animation2 = Instance.new("Animation")
Animation2.AnimationId = "http://www.roblox.com/asset/?id=1909810268"
local Squating = Character:LoadAnimation(Animation)
local SquatMoving = Character:LoadAnimation(Animation2)
local IdleAnimation = Character:LoadAnimation(game.Players.LocalPlayer.Character.Animate.idle.Animation1)
local WalkAnimation = Character:LoadAnimation(game.Players.LocalPlayer.Character.Animate.walk.WalkAnim)
Squating.Looped = true
SquatMoving.Looped = true

game:GetService('UserInputService').InputBegan:Connect(function(input,IsTyping)
	if IsTyping then return end
	local KeyPressed = input.KeyCode
	if KeyPressed == Enum.KeyCode.LeftControl then
		ControlHolding = true
		WalkSpeed = 0 --This! Also i printed it, he shows me 0 too.
		if MoveHolding == true then
			WalkAnimation:stop()
			IdleAnimation:stop()
			SquatMoving:play()
		else
			SquatMoving:stop()
			WalkAnimation:stop()
			IdleAnimation:stop()
			Squating:play()
		end
	end

function onKeyRelease(inputObject,gameProcessed)
	if inputObject.KeyCode == Enum.KeyCode.LeftControl then
		ControlHolding = false
		Squating:stop()
		SquatMoving:stop()
		WalkSpeed = 15 --Here gets problem too maybe?
	end
end
game:GetService("UserInputService").InputEnded:connect(onKeyRelease)

Yes i actually making a squating script, and i just can't change player's speed! I want to know why. By the way this is not all my codes. And Thanks for helping!

WalkSpeed is the variable not the walkspeed of the humanoid meaning you only set the variable and not the walkspeed of the humanoid.

All you need to do is set the WalkSpeed property.

local Player = game:GetService('Players').LocalPlayer -- best to use get service
local Character = Player.Character or Player.CharacterAdded:Wait() -- the player can take time to load in so get the player character if it or wait for it if the character is nil
local Humanoid = Character:WaitForChild('Humanoid')

.... 

game:GetService('UserInputService').InputBegan:Connect(function(input)
	if KeyPressed == Enum.KeyCode.LeftControl then
		Humanoid.WalkSpeed = 0 -- set walk speed
	end
end)

game:GetService("UserInputService").InputEnded:Connect(function(input)
	if KeyPressed == Enum.KeyCode.LeftControl then
		Humanoid.WalkSpeed = 16 -- set back
	end
end)

I hope this helps.