Hello Wolf2000,
Your help (the reference to Bram77) didn't work for me (the last statement)
service openmediavault restart
Failed to restart openmediavault.service: Unit openmediavault.service failed to load: No such file or directory.
aptitude install openmediavault
leads to reinstall, but then the new version 3.0.15.
So I can use the GUI, without FTP and with the 5 minute timeout-limit.