Nextcloud redirect with nginx

Hi, I have a proxmox node and on it, I have 2 LXC containers. In one of them I have a Nextcloud installation (up and running and visible from the internet) and in the other one I have a nginx server. In my work all ports are blocked except 80 and 443 (for security reasons) and, to access my Nextcloud from the Internet, I have to type nextcloud.someddns.org:1234. Since all ports are blocked, I can’t reach my Nextcloud. So I would like to use the nginx to redirect the Nextcloud front-end (lets say is in the ip 192.168.1.10:9000) in a way that I type nextcloud.someddns.org from my work and reach the Nextcloud front-end (let’s assume that I already have the NAT forwarding that send the 1234 port to the internal 9000 port).
Googling, I found that It can be done adding the configuration script I left below, in the /etc/nginx/sites-available/nextcloud file. The thing is that, in that case, the nginx and Nextcloud are in the same server. That way I can reach de Nextcloud login screen but always says wrong password (even if it is right). I guess the problem lies in the ssl certificates (because the nginx server has nothing in the /etc/ssl/nginx/ folder).
Here is the nginx script that I found, and I thank all of you who can throw some light on this matter.


upstream php-handler {
server 192.168.1.10:9000;
#server unix:/var/run/php/php7.4-fpm.sock;
}

server {
listen 80;
listen [::]:80;
server_name cloud.example.com;
# enforce https
return 301 https://$server_name:443$request_uri;
}

server {
listen 443 ssl http2;
listen [::]:443 ssl http2;
server_name nextcloud.someddns.org;

ssl_certificate /etc/ssl/nginx/cloud.example.com.crt;
ssl_certificate_key /etc/ssl/nginx/cloud.example.com.key;

includeSubDomains; preload;" always;

add_header Referrer-Policy "no-referrer" always;
add_header X-Content-Type-Options "nosniff" always;
add_header X-Download-Options "noopen" always;
add_header X-Frame-Options "SAMEORIGIN" always;
add_header X-Permitted-Cross-Domain-Policies "none" always;
add_header X-Robots-Tag "none" always;
add_header X-XSS-Protection "1; mode=block" always;

fastcgi_hide_header X-Powered-By;

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

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;

# The following rule is only needed for the Social app.
# Uncomment it if you're planning to use this app.
#rewrite ^/.well-known/webfinger /public.php?service=webfinger last;

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

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

# Enable gzip but do not remove ETag headers
gzip on;
gzip_vary on;
gzip_comp_level 4;
gzip_min_length 256;
gzip_proxied expired no-cache no-store private no_last_modified no_etag auth;
gzip_types application/atom+xml application/javascript application/json application/ld+json application/manifest+json application/rss+xml application/vnd.geo+json application/vnd.ms-fontobject application/x-font-ttf application/x-web-app-manifest+json application/xhtml+xml application/xml font/opentype image/bmp image/svg+xml image/x-icon text/cache-manifest text/css text/plain text/vcard text/vnd.rim.location.xloc text/vtt text/x-component text/x-cross-domain-policy;

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

location / {
    rewrite ^ /index.php;
}

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\/.+|oc[ms]-provider\/.+|.+\/richdocumentscode\/proxy)\.php(?:$|\/) {
    fastcgi_split_path_info ^(.+?\.php)(\/.*|)$;
    set $path_info $fastcgi_path_info;
    try_files $fastcgi_script_name =404;
    include fastcgi_params;
    fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
    fastcgi_param PATH_INFO $path_info;
    fastcgi_param HTTPS on;
    # Avoid sending the security headers twice
    fastcgi_param modHeadersAvailable true;
    # Enable pretty urls
    fastcgi_param front_controller_active true;
    fastcgi_pass php-handler;
    fastcgi_intercept_errors on;
    fastcgi_request_buffering off;
}

location ~ ^\/(?:updater|oc[ms]-provider)(?:$|\/) {
    try_files $uri/ =404;
    index index.php;
}

# Adding the cache control header for js, css and map files
# Make sure it is BELOW the PHP block
location ~ \.(?:css|js|woff2?|svg|gif|map)$ {
    try_files $uri /index.php$request_uri;
    add_header Cache-Control "public, max-age=15778463";
    # Add headers to serve security related headers (It is intended to
    # have those duplicated to the ones above)
    # Before enabling Strict-Transport-Security headers please read into
    # this topic first.
    #add_header Strict-Transport-Security "max-age=15768000; includeSubDomains; preload;" always;
    #
    # WARNING: Only add the preload option once you read about
    # the consequences in https://hstspreload.org/. This option
    # will add the domain to a hardcoded list that is shipped
    # in all major browsers and getting removed from this list
    # could take several months.
    add_header Referrer-Policy "no-referrer" always;
    add_header X-Content-Type-Options "nosniff" always;
    add_header X-Download-Options "noopen" always;
    add_header X-Frame-Options "SAMEORIGIN" always;
    add_header X-Permitted-Cross-Domain-Policies "none" always;
    add_header X-Robots-Tag "none" always;
    add_header X-XSS-Protection "1; mode=block" always;

    # Optional: Don't log access to assets
    access_log off;
}

location ~ \.(?:png|html|ttf|ico|jpg|jpeg|bcmap|mp4|webm)$ {
    try_files $uri /index.php$request_uri;
    # Optional: Don't log access to other assets
    access_log off;
}

}