Flutter chat apps using node.js with mongodb

I want a realtime chat apps on following "requirement" 1-server language (node.js [login to view URL],mongodb,expressjs,mongoose) 2-apps langauge flutter (front end part provided by us which is ready) 3-firebase notification required. Project condition:- 1-no adavance payment 2-1st you have to make simple basic chat with online and offline system on node.js with firebase notification (firebase is require only for notification) If you fullfil this 2 condition We will award u this contract (Contract amt 15000 to 25000) Time:- complition period one months (no extra time)