Firebase online to Android offline datastore

I am building a mobile app to allow for real time messaging, befriending users, creating groups to both chat and share images with, as well as creating events where users can invite one another.

I have chosen to use Firebase as the online back-end. But, given Firebase uses a NoSQL data model, while Android SQLite uses SQL, when saving data offline in Android what is the conventional way to handle this? Is there a simple way to convert or simply save from NoSQL to SQL, or do I need to build a converter?

(This is especially important for the events, as once created, they must be scheduled in the AlamManager, giving users alerts upon event time)