Thanks for the hints, guys!
Is there any way to interrupt the boot and access the command line or change the config files from NOOBS and set the system so that it does not start the GUI, but the command line?
Thanks again.
Hi experts, after a bad interrupted "sugo get-update" on my Pi3 with Raspbian Jessie, now I can access the GUI after booting it, but it has no background anymore, the time goes on on the taskbar, the LAN cable seems to exchange data but I can't move anymore the cursor via the small keyboard+touchpad...