Nothing works and I have tried no less that 6 downloads / methods of installation. 12.04 did not do this. There is literally nothing on the screen except the colourful background and the mouse.
The only way I get out of the problem is to hit Ctrl+Alt+Del and logging out. The top tool bar then shows up and I can shut down or log in again. But once I am logged in there is nothing but the mouse pointer.
For now I am going back to 12.04 because it worked.