If you downloaded the game through the Google Play Store, you can manually configure settings to prevent unintended purchases. 

Please refer to the instructions below for detailed steps:   

■  How to Set a Purchase Password in Google Play 

1. Open the Google Play Store and tap on your profile picture at the right of the search bar. 

2. Go to Settings → User Controls → Require authentication for purchases. 

3. Select 'Require authentication for every purchase through Google Play on this device.' 

4. Set up a payment password for your Google account.