NGNIX Reverse Proxy and Alexa usage with Mikrotik router

Configuration
,
1

Unfortunately I have big problems setting up the reverse proxy.
I especially need the function to use the Ecowitt integration.
Everything worked when used with Fritzbox and rebind protection there.
Now I have a new router (Mikrotik). It is not so easy to install the rebind protection here.
I’ve been trying to do this with the hairpin option for weeks.
Unfortunately unsuccessful.

Now I remembered NGINX as an option.
Here is the biggest problem. As soon as I made the necessary changes

 cors_allowed_origins:
        - https://google.com
        - https://www.home-assistant.io
    ip_ban_enabled: true
    login_attempts_threshold: 5  
    use_x_forwarded_for: true
    trusted_proxies:
      - 172.30.33.0/24

and As soon as I delete the lines:

   ssl_certificate: /ssl/fullchain.pem
     ssl_key: /ssl/privkey.pemt

Alexa can no longer access the home assistant. Hope someone has an idea.
Thx