Just as Mudpie said, you really need to get rid of fullbright.
Also, I didn't encounter and errors with shiny textures (I always have mat_specular set to 1).
Anyway, on proper feedback:
To start off, you have no info_observer_point. info_observer_points are "cameras" spectators (or dead people) can look through in the case of no players alive remaining, and by default, your info_observer_point is at the coordinates 0 0 0 at the moment.
Now onto the fullbright.
You might ask yourself, "Why would I still need lights when my map's fully lit?"
Plot twist: it isn't fully lit.
How comes?
This is your map with fullbright enabled:
This is your map with fullbright disabled:
Yup, pitch dark.
Anyway, let's get moving.
I have looked around your map and I have found some poorly placed props. Possibly because you thought it looked good in a certain angle, or you didn't make the grid small enough.
Another thing that you should consider is adding player clips to your stairs, so that a player's screen doesn't vibrate with every step taken.
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I hope you will improve your map and yourself as a mapper.

(Even though I only have 3 maps under my belt.)