Help With A Sprinting Script?

Hello SH, ive got some trouble with a sprinting script help would be appriciated. the problem is that both functions execute inside of function onKeyPress. ive tried to prevent it and even done some debugging but i cant figure out how to prevent it.

--Variables player = script.Parent.Parent.Character sprinting = false stamina = 100 maxstamina = 100 devisionvalue = script.Parent.Parent.PlayerGui.Bars.HpBarFrame.dv.Value SBar = script.Parent.Parent.PlayerGui.Bars.HpBarFrame.StaminaBar Sl = script.Parent.Parent.PlayerGui.Bars.HpBarFrame.StaminaText

--Functions function start() --Stamina Bar SBar.Size = UDim2.new(stamina / devisionvalue,0,0, 20)

--Stamina Bar Label
Sl.Text = "Stamina: " .. stamina .. "/" .. maxstamina

end

start()

function onKeyPress(actionName, userInputState, inputObject)

    if sprinting == false then
    player.Humanoid.WalkSpeed = 40
    sprinting = true
    stamina = stamina -5
    print("executed1")
    redraw()
    return
    end

    if sprinting == true then
    player.Humanoid.WalkSpeed = 16
    sprinting = false
    print("executed2")
    redraw()
    return
    end

end

function redraw() --Stamina Bar SBar.Size = UDim2.new(stamina / devisionvalue,0,0, 20)

--Stamina Bar Label
Sl.Text = "Stamina: " .. stamina .. "/" .. maxstamina

end

--Hooks game.ContextActionService:BindAction("keyPress", onKeyPress, false, Enum.KeyCode.LeftShift)

Thanks, ScrappyHaxor