Help in in implementing admob interstitial ad after the splash screen in my android app.

I have already build an android studio project with splash screen and interstitial ad code. When the user opens the app “SplashScreen” activity opens. That time the ad should start loading and when the ad loads it should show to the user immediately. After that when the user closes the ad we should be taken to the main activity. Also the ad should show every time we open the app. It should be not like that sometimes it shows and sometimes it does not. Hence I need an exert experienced in this field.