Your visual issues are the result of having gotten the camera to a preposterous position that is masked by the parallel projection because in parallel projection zoom involves scaling of the screen not moving the camera. That is, the zoom scale on the display tells you nothing about how far away the camera may be located. This is one reason I always work in perspective, reserving parallel for when orthographic views are needed on output. In your model the camera is at
eye = ( -20761’ 3 11/16", 17046901’ 10 41/64", 278541543’ )
The camera’s eye point is so far from the model that the OpenGL library’s handling of z-distance is putting everything in the same distance bin. Hence, everything shows at once. Also, it is causing “z-fighting” (flashing patterns as you orbit the camera) between faces that actually have some separation between them because the separation is negligible compared to the distance from the camera. This is an extreme example of how edges can “bleed through” a thin object in front of them when far from the camera.
The simplest way to fix the camera is to change to perspective projection (which will cause the view to zoom way out because it doesn’t move the camera!), drag a selection box around the model contents, and then right-click and choose “zoom selection”. At that point all those mysterious edges will cease to show through and the z-fighting will be gone.
And, as @Geo pointed out, you need to learn to use SketchUp’s layers correctly. You have 47830 edges and faces associated with other than Layer0. Since all of them will intersect and stick to each other despite the layers, this is a recipe for disaster! Only associate component instances, groups, text, dimensions, and images with other than Layer0. Always draw edges, faces and things made from them (such as circles, arcs, rectangles, etc.) with Layer0 active and leave them there.