Always enable Two-Factor Authentication (2FA) wherever it is possible which is not going to give 100 protection but will act as an added security layer which is always a good thing to have but never choose the Google authenticator for such purpose because we all know how google sucks our privacy.

So there are some open source 2FA apps available

Aegis Authenticator ^{Android, F-droid}
Tofu Authenticator ^iOS

And don't forget to encrypt your files which can be done using encryption software or available as built in feature too on some devices.