Setting app Nginx + WHM + cPanel

I have a backend NestJS app runs on localhost:3000I can access the app via the terminal crl http://localhost:3000 with no issue.This app must be accessed from the internet using https://api.xxxx.com and it should response 'Hi I'm here'.The issue is that when try to access https://api.xxxx.com I got the index.html content not the app response.I edited the nginx config files and it works but the configuration wiped each time the server restarted.Looking for a solution.I'm using Lamalinux9 and the Nginx is already installed (EasyApache4).I can provide you with Anydesk access to my PC to sort it out.

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Is this project for business or personal use? Personal
What information should successful freelancers include in their application? Experience
How soon do you need your project completed? ASAP