My adressbook in Android

Thunderbird for Android looks up email addresses stored in your default Android contacts app, such as google contacts. You should use that app to make additions and amendments. Ensure you've granted TB-A permission to read your contacts to use the feature. The app doesn't have its own built in address book. There are a selection of 3rd party apps on google play and other stores that support synchronising your android contacts. Davx5 is one example. https://f-droid.org/packages/at.bitfire.davdroid/ https://play.google.com/store/apps/details?id=at.bitfire.davdroid