Couple of mapping questions

1- How do I get that volumetric spotlighty effect?
2- What’s the difference between normal and fast vvis?

1 - Use a point_spotlight. It doesn’t emit light by itself so you need to add a light too.
2 - VVis calculates which areas of your map can “see” each other so only the areas the player sees are rendered. If you run fast vvis everything is rendered all the time which is bad for the performance. Type “mat_wireframe 3” in the console so you can see the difference.