Problem with nginx

Hello i have my nextcloud site in /var/www/nextcloud, with user and group www-data.
Using: ubuntu 18.04 with nginx 1.14 server.
I created local virtual host nextcloud,aaron.com

But when i go in browser to that address i get

Also my nginx in conf.d is empty.
My nginx/sites-avalaible config file:

server {
    listen 80;
    server_name nextcloud.aaron.com;
 
    # Add headers to serve security related headers
    add_header X-Content-Type-Options nosniff;
    add_header X-XSS-Protection "1; mode=block";
    add_header X-Robots-Tag none;
    add_header X-Download-Options noopen;
    add_header X-Permitted-Cross-Domain-Policies none;
    add_header Referrer-Policy no-referrer;

    #I found this header is needed on Ubuntu, but not on Arch Linux.
    add_header X-Frame-Options "SAMEORIGIN";

    # Path to the root of your installation
    root /var/www/nextcloud;

    access_log /var/log/nginx/nextcloud.access;
    error_log /var/log/nginx/nextcloud.error;

    location = /robots.txt {
        allow all;
        log_not_found off;
        access_log off;
    }

    # The following 2 rules are only needed for the user_webfinger app.
    # Uncomment it if you're planning to use this app.
    #rewrite ^/.well-known/host-meta /public.php?service=host-meta last;
    #rewrite ^/.well-known/host-meta.json /public.php?service=host-meta-json
    # last;

    location = /.well-known/carddav {
        return 301 $scheme://$host/remote.php/dav;
    }
    location = /.well-known/caldav {
       return 301 $scheme://$host/remote.php/dav;
    }

    location ~ /.well-known/acme-challenge {
#location ^~ /.well-known/acme-challenge/
      allow all;
      default_type "text/plain";
    }

    # set max upload size
    client_max_body_size 512M;
    fastcgi_buffers 64 4K;

    # Disable gzip to avoid the removal of the ETag header
    gzip off;

    # Uncomment if your server is build with the ngx_pagespeed module
    # This module is currently not supported.
    #pagespeed off;

    error_page 403 /core/templates/403.php;
    error_page 404 /core/templates/404.php;

    location / {
       rewrite ^ /index.php$uri;
    }

    location ~ ^/(?:build|tests|config|lib|3rdparty|templates|data)/ {
       deny all;
    }
    location ~ ^/(?:\.|autotest|occ|issue|indie|db_|console) {
       deny all;
     }

    location ~ ^/(?:index|remote|public|cron|core/ajax/update|status|ocs/v[12]|updater/.+|ocs-provider/.+|core/templates/40[34])\.php(?:$|/) {
       include fastcgi_params;
       fastcgi_split_path_info ^(.+\.php)(/.*)$;
       fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
       fastcgi_param PATH_INFO $fastcgi_path_info;
       #Avoid sending the security headers twice
       fastcgi_param modHeadersAvailable true;
       fastcgi_param front_controller_active true;
       fastcgi_pass unix:/run/php/php7.2-fpm.sock;
       fastcgi_intercept_errors on;
       fastcgi_request_buffering off;
    }

    location ~ ^/(?:updater|ocs-provider)(?:$|/) {
       try_files $uri/ =404;
       index index.php;
    }

    # Adding the cache control header for js and css files
    # Make sure it is BELOW the PHP block
    location ~* \.(?:css|js)$ {
        try_files $uri /index.php$uri$is_args$args;
        add_header Cache-Control "public, max-age=7200";
        # Add headers to serve security related headers (It is intended to
        # have those duplicated to the ones above)
        add_header X-Content-Type-Options nosniff;
        add_header X-XSS-Protection "1; mode=block";
        add_header X-Robots-Tag none;
        add_header X-Download-Options noopen;
        add_header X-Permitted-Cross-Domain-Policies none;
        add_header Referrer-Policy no-referrer;
        # Optional: Don't log access to assets
        access_log off;
   }

   location ~* \.(?:svg|gif|png|html|ttf|woff|ico|jpg|jpeg)$ {
        try_files $uri /index.php$uri$is_args$args;
        # Optional: Don't log access to other assets
        access_log off;
   }
}

Also just in case my /ect/hosts:
|127.0.0.1|localhost|
|127.0.0.1|nextcloud.aaron.com|
|127.0.1.1|aaron-VirtualBox|

I think everythig is ok, and i dont know the error …

Also made a ln from /etc/nginx/sites-enabled/nextcloud.aaron.com to the config file in /etc/nginx/sites-avalaible

Any help would be apreciated…

Your Nginx config does not include the necessary changes due do a Nginx + php-fpm security issue, see: Urgent security issue in NGINX/php-fpm

Your hosts file has two conflicting entries (same IP), I would add your external domain as alias (or the other way round, your local hostname as alias instead) for 127.0.1.1, so 127.0.0.1 is used for localhost only? Not sure who two entries with same IP are handled, I guess one just overrides the other.

I just want that when i go to localhost or default value go to /var/www/html and when i want to enter in nextcloud, then i should write nextcloud.aaron.com and go to content in /var/www/nextcloud … I think i have it right but it doesnt work…

This looks like a good solution to use different vhosts based on input domain: https://serverfault.com/a/832474

As long as the domain points to your server, this should be independent from /etc/hosts, where AFAIK still every IP must only appear one time, hence merge two lines with e.g. making the domain an alias of hostname or give it a dedicated 127 IP, which should all be treated as loopback.