Beginners Questions • [Installation] Need help with NGINX setup for subdomain

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### You should look at the following URL's in order to grasp a solid understanding# of Nginx configuration files in order to fully unleash the power of Nginx.# https://www.nginx.com/resources/wiki/start/# https://www.nginx.com/resources/wiki/start/topics/tutorials/config_pitfalls/# https://wiki.debian.org/Nginx/DirectoryStructure## In most cases, administrators will remove this file from sites-enabled/ and# leave it as reference inside of sites-available where it will continue to be# updated by the nginx packaging team.## This file will automatically load configuration files provided by other# applications, such as Drupal or Wordpress. These applications will be made# available underneath a path with that package name, such as /drupal8.## Please see /usr/share/doc/nginx-doc/examples/ for more detailed examples.### Default server configuration#server {listen 80 default_server;listen [::]:80 default_server;# SSL configuration## listen 443 ssl default_server;# listen [::]:443 ssl default_server;## Note: You should disable gzip for SSL traffic.# See: https://bugs.debian.org/773332## Read up on ssl_ciphers to ensure a secure configuration.# See: https://bugs.debian.org/765782## Self signed certs generated by the ssl-cert package# Don't use them in a production server!## include snippets/snakeoil.conf;root /var/www/html;# Add index.php to the list if you are using PHPindex index.html index.htm index.nginx-debian.html;server_name _;location / {# First attempt to serve request as file, then# as directory, then fall back to displaying a 404.try_files $uri $uri/ =404;}# pass PHP scripts to FastCGI server##location ~ \.php$ {#include snippets/fastcgi-php.conf;### With php-fpm (or other unix sockets):#fastcgi_pass unix:/run/php/php7.4-fpm.sock;## With php-cgi (or other tcp sockets):#fastcgi_pass 127.0.0.1:9000;#}# deny access to .htaccess files, if Apache's document root# concurs with nginx's one##location ~ /\.ht {#deny all;#}}# Virtual Host configuration for example.com## You can move that to a different file under sites-available/ and symlink that# to sites-enabled/ to enable it.#server {server_name csarena.online www.csarena.online [IP];root /var/www/csarena.online;index index.html;error_page 404 =200 /index.html;    # Deny access to hidden files (beginning with a period)    location ~ /\. {        access_log off; log_not_found off; deny all;   }location / {try_files $uri $uri/ =404;}location ~* \.(ico|pdf|flv|jpg|jpeg|png|gif|js|css|swf)$ {    expires 1h;    add_header Cache-Control "public, no-transform";}    listen [::]:443 ssl ipv6only=on; # managed by Certbot    listen 443 ssl; # managed by Certbot    ssl_certificate /etc/letsencrypt/live/csarena.online/fullchain.pem; # managed by Certbot    ssl_certificate_key /etc/letsencrypt/live/csarena.online/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 ($host = www.csarena.online) {        return 301 https://$host$request_uri;    } # managed by Certbot    if ($host = csarena.online) {        return 301 https://$host$request_uri;    } # managed by Certbotlisten 80;listen [::]:80;server_name csarena.online www.csarena.online [IP];    return 404; # managed by Certbot}