Since we still have a few hours until tomorrow, try this:
Leave the command line window on the desktop, open Task Manager (Ctrl + Shift + Esc), and kill all explorer.exe tasks. Your desktop will go blank, except for the windows already open.
Now try to delete the offending folder with rd H:\Florian\Backup\Pictures\NewJersey
After that, in the command line window enter:
explorer
to restart your desktop.
If you closed the command line window, you can still restart explorer by opening the Task Manager by holding down the Ctrl and Shift keys and briefly pressing the Esc key. In Task Manager select Applications, New Task and enter: explorer