Nginx multiple DNS to same webserver - node.js

Question

GOAL https://imgur.com/a/A04qrXz
^ Trying to get multiple (different) domains pointing at the same IP, serving the same files to bypass DNS filtering agent GoGaurdian.
Webserver SRC : https://github.com/Zaydo123/html-game-server
Why: trying to bypass a DNS filtering service
My /etc/nginx/conf.d/physics.conf (works fine)
server {
server_name physics-central.com;
location / {
proxy_pass http://localhost:3000/;
proxy_set_header X-Real-IP $remote_addr;
}
listen [::]:443 ssl ipv6only=on; # managed by Certbot
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/physics-central.com/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/physics-central.com/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
}
server {
if ($host = physics-central.com) {
return 301 https://$host$request_uri;
} # managed by Certbot
listen *:80 default_server;
listen 8000 default_server;
listen [::]:80 default_server;
server_name physics-central.com;
return 301 https://physics-central.com$request_uri; # managed by Certbot
}
Problem
From my little knowledge of Nginx, I assume I need to create one .conf file for each domain. Each is essentially the same but has different SSL certs and domain names. I tried doing this but upon reloading I received this warning/error.
nginx: [emerg] a duplicate default server for 0.0.0.0:80 in /etc/nginx/conf.d/physics.conf:27
My question
Am I going about this wrong? Am I supposed to even be making conf.d files for each domain? It would be amazing if you could help me out. Thanks.