Why does it appear like this?

Hi does anyone knows why it appear like this. I just want the faces normal
thanks

Hit K on your keyboard.
or View > Edge Style > Back Edges

Looks as if you accidentally tapped the k key on the keyboard. It toggles bacK edges on or off.

Tap k against, as @mihai.s has already suggested, to turn them off.

thanks a lot. Now it is ok