unable to start any application after migration of an user per Migration Assistant

Could not open Menu items, nothing is selectable. Reinstallation by using the recovery mod also can't be started, because the button is grayed out. Mouse is moving, but clicking has no effect. Fsck in singlemode was done with out errors. System: macOS High Sierra iMac 2011 There is no way to open any application. I can log in, the Desktop appears, but has no function. Moving the mouse over the dock, no reaction. The imported user has Admin rights. he came from a system macOS 10.6 are there any plist files overwritten? It looks like the System is locked. Is there a way to reset the computer, using single mode? All GUI system won't work.