Nintendo 3ds XL hung up what to do?

Aldo I jabe a Nintendo 3ds XL and have been playing for 5 years or so. But today he hung up so I have tomodatschi life played saved and pressed the button until I noticed later that he is not out. So the screen is black but the buttons are still lit and I can't do anything. I pressed the button again and tried to do something but nothing changes. Is there any emergency switch or what should I do?

Keep the button out long, should work.

Oh, thank you ^^