I have concerns regarding the private data of my guests and the GDPR
The registration data of your guests are freely selectable. This means that you do not have to enter the real name or a real phone number (DSVGO) to be added to the group. Of course, clear names and telephone numbers are more unique, but you can also use a room number, for example. Furthermore the entered data will be anonymized after dissolving the group and are therefore useless.