Admob interstitial workaround

Hey there!
I use this workaround to display admob interstitials:

It works great!! But my problem is, that if someone has slow internet connection, it takes some time to be displayed. But the user is already clicking in the APP and its annoying when the ad displays later.

So, does anyone have an idea how I could edit the code to check, if the ad is finished with initialization and only then show the ad manually?!

Thanks for help :v:t3: