Modyfying Existing Android Chat for Crashes

Looking for an android developer to resolve the issues of firebase based chat module of our android app. Detailed description: Me and my friend are currently working on a social media application which allows users to chat and group chat once they are connected. We are presently facing crash issues and excessive bandwidth/data usage due to realtime delivery of the entire chat messages that have been exchanged between the users since the initiation of the chat. We are looking for somebody who can share prebuilt/ custom made source code which can be integrated into our app with the following features for our chat application similar to whatsapp. 1) Creation of groups for group chats – we presently have it but we are facing constant crashes with it 2) Local storage of the entire chat on the device alongwith entry of the last exchanged message. 3) Option to backup chat on manual/ automatic basis (like weekly/monthly) to a predefined storage. I would like to work with somebody who has previously worked on a similar project. Looking to begin the project ASAP. Please send your quotations and timeline alongwith details of your previous projects similar to this one.