My stamina value doesn't change.. Why is that?

I am not sure why it doesn't work, it has been giving me problems and I don't know what the problem is so I can't learn from my mistakes.

local timeyouahavebeenrunning = 100

RunService.RenderStepped:Connect(function()
    local maxstamina = 0
    local StartingStamina = 100

    print(timeyouahavebeenrunning)
    if Userinputservice:IsKeyDown(Enum.KeyCode.LeftShift) and humanoid.MoveDirection.Magnitude > 0  and Debounce == true then


        if  timeyouahavebeenrunning <= maxstamina then
                local Debounce = false
        else
            humanoid.WalkSpeed = 23
            camera.FieldOfView = 80
            RunService.RenderStepped:Connect(RunningEffect)
            while timeyouahavebeenrunning <= maxstamina  do
                wait(0.25)
                timeyouahavebeenrunning = timeyouahavebeenrunning - 1
            end
        end
    else
        if timeyouahavebeenrunning >= StartingStamina then
            local Debouce = true
        else
            humanoid.WalkSpeed = 16
            camera.FieldOfView = 70
            RunService.RenderStepped:Connect(updateBobbleEffect)
            if timeyouahavebeenrunning > maxstamina then
                while humanoid.MoveDirection.Magnitude > 0 and Userinputservice:IsKeyDown(Enum.KeyCode.LeftShift) or timeyouahavebeenrunning >= StartingStamina do
                    wait(0.25)
                    timeyouahavebeenrunning= timeyouahavebeenrunning + 1
                end

                if humanoid.MoveDirection.Magnitude > 0 and Userinputservice:IsKeyDown(Enum.KeyCode.LeftShift) then
                    local Debounce = true
                end

            else
                        while timeyouahavebeenrunning >= StartingStamina do
                        wait(0.25)
                        timeyouahavebeenrunning = timeyouahavebeenrunning - 1

                    end
                end

            end
        end

end)