Help needed for app deployment

I have deployed my app using firebase. It is deployed successfully but backend is not working. Please help.
See Live app here:-

Hi Kuljeet,
If you took code directly from an educative playground the files are connected but when run your app locally or deploy it needs to call the CSS and JS files from your html file. I’ll put an example below. If you name your JS file app.js and your CSS file styles.css this will work. They also need to be at the same level in the directory. Adjust if you have placed them in a folder or named them something else.

<!-- your html here for chat app -->

<script src="app.js"></script>