Need help with some connection Issues mostly when connected to VPN

[TeamTiger]

Hi there, I have some issues accessing running Docker services when i activate when i am connected to my VPN.

Issue 1.
For example with my Adminer docker.
When VPN is On then i can acces the webui only locally using IP:port!
When using Hostname i get error 522

When VPN is OFF then i can acces the webui locally using IP:port and Hostname and remotely only with Hostname.
This is the same for my Nextcloud Docker.

Issue 2.
Even following guides from SpaceInvaders or Ibrocorp to the letter
I cannot get secure acces to NPM and also not through Hostname
I can only acces the webui locally by IP:port
This is also the same for some other dockers.

The Setup.
Asus Router (OpenVPN Client connected) 
using Cloudflare and NGINX for Hostname and reverse proxy
have Cloudflare-DDNS docker to update the Dynamic ISP.

Hope that someone can tell me what i have to change or did wrong.