Making a new view controller appear after interstitial ad is dismissed - swift

Question

I am building an iOS app in swift with Xcode that has a button that, when pressed, will (among other things) show an interstitial Admob ad, and then go to a different view controller. Right now, when I press the button, an interstitial ad will appear. However, when I close the ad, the view is still on the original page. If I click the button again, then I am taken to the second view controller. Sometimes, however, I have to dismiss three or four ads before I get to the second view controller. How can I make it so that, after I dismiss the interstitial ad, I go straight to the second view controller?
Here is the current code:
#IBAction func postPressed(_ sender: Any) {
if contact.text?.isEmpty == true {
print("No contact")
return
}
if avail.text?.isEmpty == true {
print("No availability")
return
}
uploadSpot()
}
func uploadSpot() {
let key = Int.random(in: 20001..<30000)
let object: [String: Any] = [
"Contact": contact.text!,
"Availability": avail.text!,
]
geoFireRef.child("\(key)").setValue(object)
let location = manager.location!
geoFire.setLocation(location, forKey: "\(key)")
if interstitialAd?.isReady == true {
interstitialAd?.present(fromRootViewController: self)
}
let storyboard = UIStoryboard(name: "SpotLoaded", bundle: nil)
let vc = storyboard.instantiateViewController(identifier: "SpotLoaded")
vc.modalPresentationStyle = .overFullScreen
present(vc, animated: true)
}
The import part is in the function "uploadSpot()," where
if interstitialAd?.isReady == true {
interstitialAd?.present(fromRootViewController: self)
}
presents the ad and
let storyboard = UIStoryboard(name: "SpotLoaded", bundle: nil)
let vc = storyboard.instantiateViewController(identifier: "SpotLoaded")
vc.modalPresentationStyle = .overFullScreen
present(vc, animated: true)
switches the viewcontroller. I have tried reversing the order if these two (i.e. putting let storyboard, etc., before if insterstitialAd), but that just takes me to the new view controller and the ad never appears. I have also tried putting the let storyboard chunk inside of the brackets following the if interstitialAd. This does not help either. If I put it after interstitialAd?.present(fromRootViewController: self), I have the same problem where the ad shows but the view controller does not change. If I put it after, the viewcontroller changes but the ad never shows.
As the main purpose of interstitial ads is to appear in between views of an app, I do not think what I am trying to do should be so difficult. I think there must just be something I am missing or do not understand. Please help in whatever way you can.