Meanwhile I got it
I edited /etc/rsyslog.conf
I put this text to module section
module(load="imfile" PollingInterval="10")
And this to the rule section
# File 1
input(type="imfile" File="/var/log/proxmox-backup/api/auth.log"
Tag="tag1"
StateFile="/var/log/proxmox-backup/api/state.log"
Severity="notice"
Facility="local0")
Then systemctl restart rsyslog