Hi had to work hole day with 120%, so sorry for late answer.
I did yum remove urbackup. In /var/urbackup are databases. I deletet them manually, otherwise urback restores old values. Also did ‘config delete urbackup-server’, ‘config delete urback-udp’ and ‘signal-event firewall-adjust’. After that, new urbackinstallation asked again for backup-folder and admin user and no client were stored anymore. So i think it was a real new installation.