Nextcloud 15 behinds a reverse proxy(nginx) gets untrusted domain message

I have set up a Nextcloud 15 in a small server in my local network( with Apache2 at port :85, and it is behind a nginx reverse proxy in :80.
Once I access it by its IP address:85, it works normally.
But when i trying to access it from port 80 or HOSTNAME.local, it shows a " Access through untrusted domain" message. I should modify trusted_domain array manually to get access.

So if I set a port forwarding to this PC, it will not work until I add the IP address to trusted_domain.

How could this situation changed? I dont want to add trusted domains one by one.
I would appreciate it very much if you could help me!

My nginx.conf is here:

server {
        listen       80;
        server_name  debian-server.local;
        location / {
            root   html;
            index  index.html index.htm;
        location /nextcloud {
        # rewrite ^/nextcloud(.*) $1 break;
        proxy_pass_header Server;

        proxy_set_header        Host                    $host;
        proxy_set_header        X-Real-IP               $remote_addr;
        proxy_set_header        X-Forwarded-For         $proxy_add_x_forwarded_for;
        proxy_set_header        X-Forwarded-Proto       $scheme;
        proxy_set_header        X-Forwarded-Host        $host;

        proxy_pass_header  Authorization;
        rewrite ^/nextcloud(.*) $1 break;

My apache site conf is here:

<VirtualHost *:85>

        ServerAdmin webmaster@localhost
        DocumentRoot /var/www/nextcloud

        ErrorLog ${APACHE_LOG_DIR}/error.log
        CustomLog ${APACHE_LOG_DIR}/access.log combined
        Alias /nextcloud "/var/www/nextcloud/"

<Directory /var/www/nextcloud/>
  Options +FollowSymlinks
  AllowOverride All

 <IfModule mod_dav.c>
  Dav off

 SetEnv HOME /var/www/nextcloud
 SetEnv HTTP_HOME /var/www/nextcloud


And, the nextcloud config.php:

$CONFIG = array (
  'instanceid' => 'removed',
  'passwordsalt' => 'removed',
  'secret' => 'removed',
  'trusted_domains' =>
  array (
          0 => '',
          1 => '',
          2 => '' // my pc's address
  'trusted_proxies' =>
  array (
        0 => ''
  'datadirectory' => '/var/www/files',
  'dbtype' => 'mysql',
  'version' => '',
  'overwrite.cli.url' => '',
  'overwritewebroot' => '/nextcloud',
  'dbname' => 'nextcloud',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'removed',
  'dbuser' => 'removed',
  'dbpassword' => 'removed',
  'installed' => true,

Information of my Server(probably):
Hostname: debian-server.local
Nextcloud Version: 15.0.4
OS: Debian 9.7 stretch amd64
Apache version: Apache/2.4.25(debian)
Nginx version: 1.15.8

You need to add HOSTNAME.local to your trusted_domains in nextcloud config.

Also, you may want to remove your instanceid, passwordsalt and secret in your post.

Thank you for your notice. I have removed these proxy_set_header s. And things goes normally.