Dont use (only) fingerprint to unlock, AS they can force you to put your finger, they can't force you to remember a password.

If possible have only Foss apps on your main profile (fdroid, neo store etc.) And one/multiple separate profile for closed source apps if you need them.

Check the tools under "security and privacy" in your pull down menu (like hardened memory allocation)

Inform yourself on what a secure system helps you with, and what not. (For example they can still hijack cellphone towers (stingray attack) and act accordingly

Did you flash gapps / Google services? If so Google will still have full control over your phone.

old joke, might be related... the space agency sends three pigs and a bro to space. they travel along their route and after a while control radios in:

control: pig 1, enable telemetry

pig 1: oink

control: pig 2, check perimeter

pig 2: oink

control: pig 3, reverse thrusters 10%

pig 3: oink

control: bro!

bro: sup

control: feed the pigs, don't touch nothin'

Congratulations! :D

Not de-Google advice perse, but I recommend using a hardware key for two factor authentication: https://www.yubico.com/

One time passwords that are received through SMS and email are interceptable. Not so much with hardware keys. Yubico also makes an authenticator app whose source code is open: https://github.com/Yubico/yubioath-flutter

One idea, though I don't know the tools for that, is to configure at system level blocks against Google's domains and DNS's.