thanks for your reply!
Here is the DYNDNS Configuration:
Yes the webservices are allowed, but i want to connect a Webstation of another client over the TRB140, so i have configured a Portforwarding in the Firewall Roules. Thats all ive changed, but it dont works yet.
The Ping in the CLI for the other Device works fine, so i think its a problem between the DYNDNS and the TRB140.