Having troubles with making doing a shift to sprint with animation?

Not sure what I did wrong but it isn't working and I need help.

local player = game.Players.LocalPlayer local Character = player.Character or script.Parent local humanoid = player.Character.Humanoid local Humanoid = Character.Humanoid local UIS = game:GetService("UserInputService")

local AnimationId = 'rbxassetid://6267230901'

UIS.InputBegan:Connect(function(input) if input.KeyCode == Enum.KeyCode.LeftShift then if player.Character ~= nil then

		while player.Character.Humanoid.WalkSpeed >= 50 do 
			wait()

			local Animation = Instance.new("Animation")
			Animation.AnimationId = AnimationId
			local LoadAnimation = Humanoid:LoadAnimation(Animation)
			LoadAnimation:Play()

		end
	end
end

end)

UIS.InputEnded:Connect(function(input) if input.KeyCode == Enum.KeyCode.LeftShift then if player.Character ~= nil then player.Character.Humanoid.WalkSpeed = 16

		while player.Character.Humanoid.WalkSpeed <= 16 do 
			wait()

			local Animation = Instance.new("Animation")
			Animation.AnimationId = AnimationId
			local LoadAnimation = Humanoid:LoadAnimation(Animation)
			LoadAnimation:Stop()

		end
	end
end

end)

Put a local script on the StarterPlayerScripts, then enter this:

repeat wait() until game.Players.LocalPlayer
local Player = game.Players.LocalPlayer
local Character = workspace:WaitForChild(Player.Name)
local Humanoid = Character:WaitForChild('Humanoid')

local AnimID = 123456789 -- put your animation ID here

local RunAnimation = Instance.new('Animation')
RunAnimation.AnimationId = 'http://www.roblox.com/asset/?id='..AnimID
RAnimation = Humanoid:LoadAnimation(RunAnimation)

Running = false

function Handler(BindName, InputState)
	if InputState == Enum.UserInputState.Begin and BindName == 'RunBind' then
		Running = true
		Humanoid.WalkSpeed = 50
	elseif InputState == Enum.UserInputState.End and BindName == 'RunBind' then
		Running = false
		if RAnimation.IsPlaying then
			RAnimation:Stop()
		end
		Humanoid.WalkSpeed = 16
	end
end

Humanoid.Running:connect(function(Speed)
	if Speed >= 10 and Running and not RAnimation.IsPlaying then
		RAnimation:Play()
		Humanoid.WalkSpeed = 50
	elseif Speed >= 10 and not Running and RAnimation.IsPlaying then
		RAnimation:Stop()
		Humanoid.WalkSpeed = 16
	elseif Speed < 10 and RAnimation.IsPlaying then
		RAnimation:Stop()
		Humanoid.WalkSpeed = 16
	end
end)

Humanoid.Changed:connect(function()
	if Humanoid.Jump and RAnimation.IsPlaying then
		RAnimation:Stop()
	end
end)

game:GetService('ContextActionService'):BindAction('RunBind', Handler, true, Enum.KeyCode.LeftShift)