Faces dissapeared (toposolid)

Hi. I am working on a topography model, but during my work, all of the faces of the model disappeared unexpectedly. I checked the display settings, which is not wireframe but shaded with textures so I dont have an idea what could went wrong. Unfortunately it seems I cant take the change back and have not a saved version of the correct terain.
I attach some pictures, one of the state before and then the current.

Maybe you could share the .skp file so we can have a look and try to help you out.

What version of SketchUp are you really using? Your profile says SketchUp for Schools. That’s a version for young school children and your screen shots prove it’s not what you are using. Please correct your forum profile.