How can I set up my network to allow for a request of Port 80 but show the domain name at the URL?

Hi!

I have a website that currently had a main page <Domain.com> that points to a web server(running Ubuntu Server) with that is port 80 I have a Synology Server that runs on port 5000(http) and 5002 (https)

I'm trying to get synology.<domain>.com to point to <public IP> :5002 and display synology.<domain>.com in the URL bar but it just changes to <public IP>:5002

I'm also trying to get CertBot to certify that subdomain, but because of this issue that I'm unsure how to solve, it won't work.

Right now I'm using a URL Redirect in the DNS (I'm using namecheap)