Build a chat part of the product for iOS and Web

I am developing an application that has personal & group chat capabilities, and requires a robust solution with push notifications, messages / images / audio messages. Users in the app will be able to chat personally, create or be added to group chats as well as be added to a channel where they can only read messages from the channel creators (similar to Telegram channels). I am looking for a person who can take on the development of the backend logic for this chat and the user interface. The designs are ready. A chat should be scalable, we are projecting 25-50k MAUs in first 6 months, the group chats should be able to accommodate up to 300 users and channels should work well with theoretically unlimited users, but likely up to 5000 users. The solution should be build to scale. The solution should be due the middle of July at most. FRONT-END: I am working in swiftUI for the iOS application and React.js for the web application. You should be working in either UIKit or swiftUI for the iOS user interface part of work / internal logic, and the framework for web app should be preferably React.js. BACK-END: We are writing a restful api in Django, but will likely use Firebase for authentication. The choice of the framework / language is up to you, but we prefer solutions built either on top of Firebase Cloud Messaging, or developed in Python / Java / Javascript. If not based on firebase, the solution should be able to be hosted on Heroku. When placing the bet, please do not list all of the unrelated skills. Please include the following information: 1) technological stack for implementing the iOS part (UIKit / SwiftUI) & examples of work 2) knowledge of React.js for implementation of the web app & examples of work 3) the technological stack for the backend logic of the chat The quality of provided information and the relevance of experience are the deciding factors. The budget is very flexible, but we expect professionalism. Please fee free to contact me with any questions. (English, Ukrainian, Russian)