Python 3.5 FireBase import error
Some newwibe tips
Rpi Rasbian 2019apr version built in python 3.5.3 is OK. Do not try to update python higher. I once tried 3.6x and made a whole mess. Of course old FireBase (and many other) packages often could not catch up new Raspbian/Python. So I always try to be humble, check the change log and use one or two stable versions older than current/beta. Also Check the FireBAse tutorials you are following to make sure if they are using old Jessie and python 2.7x. You might need to fast backward to last decade. :)
Firebase Realtime Database using Python SDK - Rakibul Islam 2018feb17
Getting Started with Cloud Firestore with Python - thatJenPerson
Perhaps you might like to let us know which Raspbian version and FireBase SDK you are using, which tutorial/instruction guide your are following etc, then we can join in debugging.
FireBase - Wikipedia
FireBase is a mobile and web application development platform
developed by FireBase in 2011, then acquired by Google in 2014.
As of October 2018, the Firebase platform has 18 products, which are
used by 1.5 million apps.