func requestForAdsInter(view: UIViewController) {
        GADInterstitialManager.shared.loadInterstitialAds { [weak self] didCompleted in
            debugPrint(didCompleted)
            self?.getNativeAdControllerInter(view: view)
        } didCompleteWithError: { didCompleteWithError in
            debugPrint("didCompleteWithError \(didCompleteWithError)")
        }
    }
    
    func loadInterstitialAds(didCompleted: @escaping successHandlerInter,
                             didCompleteWithError: @escaping errorHandlerInter) -> () {
#if DEBUG
        GADMobileAds.sharedInstance().requestConfiguration.testDeviceIdentifiers = [ testDeviceID ]
#endif
        let adUnitID = getInterstitialAdUnitID()
        GADInterstitialAd.load(withAdUnitID: adUnitID,
                               request: GADRequest(),
                               completionHandler: { [self] ad, error in
            if let error = error {
                didCompleteWithError(error.localizedDescription)
                return
            }
            interstitial = ad
            interstitial?.fullScreenContentDelegate = self
            didCompleted(true)
        })
    }

• adUnitID: Interstitial ad unit id which you got from the google console.
• viewController: where the interstitial will be visible.

		 func getNativeAdControllerInter(view: UIViewController) {
        GADInterstitialManager.shared.showInterstitialAds(
            view: view,
            didPresent: {
                debugPrint("In Present")
            },
            didDismiss: {
                debugPrint("didDismiss")
            },
            didFailToPresent: { didFailToPresentWithError in
                debugPrint("didFailToPresent")
            })
    }
func showInterstitialAds(view: UIViewController,
                             didPresent: @escaping didPresentFullScreenContent,
                             didDismiss: @escaping didDismissFullScreenContent,
                             didFailToPresent: @escaping didFailToPresentFullScreenContentWithError) -> () {
        presentFullScreenContent = didPresent
        dismissFullScreenContent = didDismiss
        failToPresentFullScreenContentWithError = didFailToPresent
        if let ad = interstitial {
            ad.present(fromRootViewController: view)
        } else {
            print("Ads was not ready")
        }
    }

		 func ad(_ ad: GADFullScreenPresentingAd,
            didFailToPresentFullScreenContentWithError error: Error) {
        print("Ads Fail to Present")
    }
    func adWillPresentFullScreenContent(_ ad: GADFullScreenPresentingAd) {
        presentFullScreenContent?()
    }
    func adWillDismissFullScreenContent(_ ad: GADFullScreenPresentingAd) {
        dismissFullScreenContent?()
    }