banner ad fixed at the bottom of page.(should be fix at bottom of mobile screen)

Question

[enter image description here](https://i.stack.imgur.com/1N2HA.png) Hi, like 2 imagines banner ad stacked at the bottom of page,, normally it should be follow up when you scroll up. what I must to do??

//AdBanner codes

override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)
        loadBannerAd()
    }
    
    override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
        coordinator.animate(alongsideTransition: { _ in
            self.loadBannerAd()
        })
    }
    
    func loadBannerAd() {
       
        let frame = { () -> CGRect in
            if #available(iOS 11.0, *) {
                return view.frame.inset(by: view.safeAreaInsets)
            } else {
                return view.frame
            }
        }()
        let viewWidth = frame.size.width

      
        bannerView.adSize = GADCurrentOrientationAnchoredAdaptiveBannerAdSizeWithWidth(viewWidth)

        bannerView.load(GADRequest())

I want normal banner ad.