Convert Existing Android Studio Project Activities to Fragments

I have an existing Android project that has multiple Activities.
I want it to be converted to a single activity with the fragments converted from the existing activities.

This project has Admob Banner and Interstitials Ads between activity loads. I want the banner to still show under the only activity (not reload following the activity load), and the interstitial action to follow its original flow.

I will provide half of the project source code. I want you to also make some comments in the source code that clearly indicate what was changed, so that I can apply it to the other half of the project's source code.
Do not remove the original code, just comment them out and make change/conversion.