How to make a stamina bar

i want to make a stamina bar that drains while running with tweening it but im not all that good with gui’s.
would anyone know how to implent this into my current code here is my code

local Stamina = 100

local SprintHeld = false
local Sprinting = false
local Exhausted = false

local RunRefresh = 20 
local SpeedDiff = 6
local DrainRate = 20 -- drain per second
local UserInputService = game:GetService("UserInputService")
local Humanoid = game.Players.LocalPlayer.Character.Humanoid
local function sprint(active)
	if Exhausted then return end -
	if active then
		Humanoid.WalkSpeed = Humanoid.WalkSpeed + SpeedDiff
	else
		Humanoid.WalkSpeed = Humanoid.WalkSpeed - SpeedDiff
	end
	Sprinting = active
end

UserInputService.InputBegan:Connect(function(input)
	if input.KeyCode == Enum.KeyCode.Z then 
		
	SprintHeld = true
	sprint(SprintHeld)
	end
end)

UserInputService.InputEnded:Connect(function(input)
	if input.KeyCode == Enum.KeyCode.Z then
		
	SprintHeld = false
	sprint(SprintHeld)
	end 
end)
local RunService = game:GetService("RunService")
RunService.Heartbeat:Connect(function(DeltaTime)
	if Sprinting then
		if Stamina > 0 then
			Stamina = Stamina - DrainRate * DeltaTime
		else
			sprint(false)
			Exhausted = true
		end
	elseif Stamina < 100 then
		Stamina = Stamina + DrainRate * DeltaTime
		if Stamina > RunRefresh then 
			Exhausted = false
			if SprintHeld then 
				sprint(SprintHeld)
			end
		end
	end
end)