What can I do?
Thank you.
What you need is to stop the container, replace the created server.key and server.pem with those provided by StartSSL(renaming them to server.key and server.pem of course), then start the container again.
It is what I have been doing for the last couple of hours, but after replacing the key and pem files, the webui stop working. It start working again if I delete the StartSSL certificate and let the container recreate the self-signed certificate.