Banner ad when clicked opens page multiple times

Hi everyone

i hope you're all doing well during this strange time

i've only just implemented ads on my game and I am having two problems

when clicking on the banner add, it opens a random amount of web pages, sometimes it opens 1 and other times 10 - 20!

my InterstitialAD plays the moment i activate it pressing a button (which is great!) but as soon as the scene starts (retry button, which then reloads the scene) the ad shows again!

I have two objects
1 with video ads script attached and another with the banner ads script

here are my scripts:
-----------------------------------------------------------------------------------------------------------------------------
Banner
-----------------------------------------------------------------------------------------------------------------------------
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Advertisements;

public class BannerAds : MonoBehaviour
{
string gameId = "xxxxx";
string myPlacementId = "banner";
bool testMode = true;

void Start()
{
Advertisement.Initialize(gameId, testMode);
StartCoroutine(ShowBannerWhenReady());
}

IEnumerator ShowBannerWhenReady()
{
while (!Advertisement.IsReady(myPlacementId))
{
yield return new WaitForSeconds(0.5f);

}
Advertisement.Banner.SetPosition(UnityEngine.Advertisements.BannerPosition.BOTTOM_CENTER);
Advertisement.Banner.Show(myPlacementId);
}
}

-----------------------------------------------------------------------------------------------------------------------------
Video Ads
-----------------------------------------------------------------------------------------------------------------------------

using UnityEngine;
using UnityEngine.Advertisements;

public class UnityMonetization : MonoBehaviour, IUnityAdsListener
{


string gameId = "xxxxx";
string myPlacementId = "rewardedVideo";
bool testMode = true;

void Start()
{
Advertisement.AddListener(this);
// Initialize the Ads service:
Advertisement.Initialize(gameId, testMode);
// Show an ad:
//Advertisement.Show();
}

public void DisplayInterstitialAD()
{
Advertisement.Show();
}

public void DisplayVideoAD()
{
Advertisement.Show(myPlacementId);
}

// Implement IUnityAdsListener interface methods:
public void OnUnityAdsDidFinish(string placementId, ShowResult showResult)
{
// Define conditional logic for each ad completion status:
if (showResult == ShowResult.Finished)
{
// Reward the user for watching the ad to completion.
Debug.LogWarning("You receive reward for watching the video");

}
else if (showResult == ShowResult.Skipped)
{
// Do not reward the user for skipping the ad.
Debug.LogWarning("You don't receive reward for skipping the video");
}
else if (showResult == ShowResult.Failed)
{
Debug.LogWarning("The ad did not finish due to an error.");
}
}

public void OnUnityAdsReady(string placementId)
{
// If the ready Placement is rewarded, show the ad:
if (placementId == myPlacementId)
{

}
}

public void OnUnityAdsDidError(string message)
{
// Log the error.
}

public void OnUnityAdsDidStart(string placementId)
{
// Optional actions to take when the end-users triggers an ad.
}

}

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Thanks for your time!