If you didn't advise me, I did it myself.
For those who want to solve it, I have a working but bad solution:
To access the web administration, I use a reverse proxy according to the settings above. For access via the application, I set up portforwarding with port 9443 in the router. The domain that points to the public IP address is written in the application. Then port 9443 is selected. It works, but it's not through a proxy and therefore so secure for communication.
But if no one gets advice, I can't do it better.
For those who want to solve it, I have a working but bad solution:
To access the web administration, I use a reverse proxy according to the settings above. For access via the application, I set up portforwarding with port 9443 in the router. The domain that points to the public IP address is written in the application. Then port 9443 is selected. It works, but it's not through a proxy and therefore so secure for communication.
But if no one gets advice, I can't do it better.