Hi 124Freibier
Its difficult to tell.
-
Did you verify the whonix images?
-
Can you try opening a virtual console.
-
Do you have enough RAM for both host and Whonix VMs? You can try freeing up RAM by shutting down non-essential processes on the host and adding RAM in VirtualBox settings.
If none of this helps could you please try creating a Debian VM in VirtualBox and see if you have the same issue.
Edit by Patrick:
See Kicksecure ™ in VirtualBox - Troubleshooting - Kicksecure ™ does not Start?