Nextcoud Talk takes a long time to connect

Nextcloud version (eg, 19.01):
Operating system and version _: Raspbian
Apache yes


I’ve been using your Nextcloud Talk application for a while.

Unfortunately, it takes a very long time to establish a connection. Sometimes it doesn’t even ring the person to be called.

And when you reach the caller, the call request is only displayed briefly on the mobile phone screen.

I cannot change the settings.

What can I do?