Proxying with nginx

Install/Maintain/Configure
1

After checking out the discourses for an answer without success…

Environment:
Public-Webserver Apache2 at 192.168.0.X redirects http to https and then via
a router to the 192.168.100.X nginx webserver which holds the letsencrypt certificate
and acts as a proxy within the .100.X net to several lxcCONTAINERS wit location directives

The problem:
there is no chance to get correct websites but 192.168.100.X:3000
every other URL gives the content but without pics and correct format.

The configs:
default at gitea.local

Default server configuration

server {
listen 80 default_server;
listen [::]:80 default_server;

root /var/www/html;

index index.html index.htm index.nginx-debian.html;

server_name _;

location / {
	try_files $uri $uri/ =404;
}
  }

server {
listen 80;
listen [::]:80;

server_name 192.168.100.36;

location / {
	proxy_pass http://192.168.100.36:3000/;
}
   }

app.ini

ROOT_URL = http://public_URL.de/ - NOPE

ROOT_URL =https://public_URL.de/ _NOPE

ROOT_URL = http://192.168.100.36/ # - NOPE

default at web.local
server {

    root /var/www/html;
    index index.html index.htm;

    server_name public_url.de www.public_url.de;

    location / {
            try_files $uri $uri/ =404;
    }

listen [::]:443 ssl ipv6only=on; # managed by Certbot
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/public_url.de/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/public_url.de/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

2021-04-02 WM

location /gitea {
            # proxy_pass http://192.168.100.X:3000;  # - NOPE
            # proxy_pass http://192.168.100.X:3000/; # - NOPE
            # proxy_pass http://192.168.100.X;           # - NOPE
            proxy_pass http://192.168.100.X/;             # - NOPE
    }

The logs:
gitea.local
gitea … no issues
nginx … no issues

nginx acces.log web.local
92.168.100.19 - - [03/Apr/2021:17:36:56 +0200] “GET /gitea/ HTTP/1.1” 404 2870 “-”
192.168.100.X - - [03/Apr/2021:17:37:57 +0200] “GET /gitea HTTP/1.1” 200 4532 “-”

Thank you. Every help is greatly appreciated and it would be goot if you implement
this problem in your install manual

willi