Thank you.
Now it looks like it's waiting for "Reading firmware data ..."
pi@Repetier-Server:~ $ sudo -u repetierserver LC_ALL=C /usr/local/Repetier-Server/bin/RepetierServer -c /usr/local/Repetier-Server/etc/RepetierServer.xml
Read configuration file /usr/local/Repetier-Server/etc/RepetierServer.xml
Testing alternative config: "/usr/local/Repetier-Server/etc/RepetierServer-extra.xml"
Testing alternative config: "/var/lib/Repetier-Server/database/RepetierServer.xml"
ServerSetting::init()
Reading server settings...
18:43:38.475: Imported external command Shutdown Server
18:43:38.475: Imported external command Reboot Server
18:43:38.475: Imported external command Restart Klipper
18:43:38.475: Imported external command Power Printer Off
18:43:38.475: Imported external command Power Printer On
18:43:38.475: Imported allowed execute command poweron
18:43:38.476: Imported allowed execute command poweroff
18:43:38.476: Webdirectory: /usr/local/Repetier-Server/www/
18:43:38.476: Storage directory: /var/lib/Repetier-Server/
18:43:38.476: Configuration file: /usr/local/Repetier-Server/etc/RepetierServer.xml
18:43:38.476: Directory for temporary files: /tmp/
18:43:38.476: Reading firmware data ...
Edit: After 10min it's still waiting at the same spot.