The black triangles might be graphics artifacts caused by a troublesome graphics driver. You might try looking on the web site of the manufacturer who provided the graphics card to see if there is a newer version of their driver (do not trust Microsoft to tell you).
@TDahl is most likely correct. But there could be other problems. If you can share the skp file, we can check whether others see the same issues or not.
Another possibility is that something in your model has “astronomical” distances, either your model is far from the origin, or parts of it are.