How to Merging Local Data With Firebase Database.

I have created a chat application with Firebase and I am not sure about how I can store my chat data locally and sync every time. when user sends a message. I dont want the user to wait until data gets updates. Cloud Functions takes 2-3 seconds for me. I want to add that data locally with a sending status

 

How to: How to show message on chat list before data gets updates to firebase cloud

 

Please have a look attached file.