Add Ads to my app

I have a simple game code source that can play on android studio and contains admob banner and interstitial an ad banner that shows below when the game starts and a banner that shows at the end of level but I have one problem is that the CTR of this ads is too low don't even ascend 1% or 1.5% and I would like to increase the power of showing ads to increase my ctr to a high pourcentage