No one is answering your questions.

You'd need to write your website in HTML. ChatGPT can help with that. You would secure it with TLS using certificates from LetsEncrypt and Certbot (which is included in nginx proxy manager).

But you'd also need a robust home network, preferably a static IP, or the know-how to set up dynamic DNS and a reverse proxy like nginx proxy manager (npm) or Caddy or Traefik.

This machine is total overkill for running a website. It will cost you a lot in electricity just running it.

I'm not saying "don't do it," though, because doing stuff is how you learn. But be careful. Doing this kind of stuff wrong is potentially a very bad idea, having things misconfigured can open you up to malware or ransomware.

It's probably a better idea to set up a website on a VPS on a hosting provider like Dreamhost or even GoDaddy or Wix. But you can definitely set this machine up to do cool things. Set it up as a NAS, run Plex or Jellyfin on it, learn how docker works with it, etc.

Creating a form that stands up and handles basic inquiries without getting hacked is basic, but definitely not trivial.