The own OS and preinstalled app in a Mobile are extracting your data. This you can only avoid to root it to be able to desinstalar them, but this cause that you must made the security updates by yourself, in rooted phones it isn’t automatic. Than use only apps from F-Droid and not from the Store, install an paid AV and use VPN. Only in this way it is somewhat more secure. Better if you use some Linux Mobile.