Firebase project

Hi, I am developing an app which is like 75% done and my earlier dev who used to do front-end and back-end moved out of the project. I need some backend dev--two to three additional functionalities and some minor work are still need to be done and the front-end development is being finished off by a frontend dev over the course of the next week, and I need backend to be ready in that time too. It is a firebase project. Front-end is reactnative for both Ios and Android app. Backend Requirements are:- 1) rework email delivery system (nodejs) which was already setup as part of cloudfunction in firebase . 2) working with frontend dev to resolve userid system that was already setup 3) storing additional user data 4) working with front end dev to resolve issues that might arise. This is more or less the gist of what needs to be done.