Help me restart Trisquel

I don't know what happened.

Ofently, Trisquel is aksing me my password to open a session.

No way this time.

I have the usual visual in the back, i have at the top of the screen the clock with the rigth hour, at the top rigth i can choose to restart or hut down my computer and a window (it is not working) and at the center of the screen a window with the trisquel logo and my username. When i click on my username this change to Trisquel 6.0.

When i want to force to shut down with the on/off button of my computer it tells :
"You are now connected as "Gnome display manager, this computer will shut down in 60 seconds".

There is NO WAY to have a normal session !!!

Please help !