Hi, Deepika,
yes, I can totally reproduce it with your sample HelloWorld app.
This is what I did.
1) I imported the HelloWorld app in both Unity and MonoDevelop.
2) I added Google Mobile Ads 3.7.0 Unity package
4) in GoogleMobileAdsDemoScript I changed line 25 with my app id and changed line 227 with my ad unit id. Also put Debug.Log("update") inside the Update() method.
5) Deployed on device. Device is Samsung Galaxy J5 (2016). Run the application with Unity profiler autoconnected.
6) App is ran on the device successfully, Profiler tracks the performance, "update" is printed in the console every frame.
7) Request interstitial.
8) Show interstitial. Interstitial is being shown. Please note that this is real interstitial as I've not enabled test ads so that I can see a real ad. Some video ad from some random game is played from Unity ads.
9) From this point on, up until I close the ad, the profiler freezes, so does the "update" print in the console.
10) I close the ad, profiler resumes, so does the "update" print in the console.
Same thing is reproducible in my game as well. Please address the issue as it is a big problem. App should not get frozen at all as I need to do background activity while interstitial is being shown.
As I said the very same setup does not result in freezing on iOS devices. Everything is fine there.
Thanks