Since it's a very open map there's only pistol ammo available.
That's a very bad excuse as it breaks the diversity of the weapons thus the gameplay.
There are a lot of open maps which contain ammo for all weapons.

The only way through the map is along clip 'corridors' marked by pathways on the ground.
1. In general there should be more than 1 way to any area within a map (unless there are certain consequences to be there like a powerup or a risky shortcut to the flag).
2. Read the commandments of Quadropolis.

Use sauer maps as example to make your own maps, this isnt even close.

At least you're giving it a go!!! Welcome to Sauer and quadropolis I guess. If you see me around ask me for some help. Otherwise, as Doko said, use some other maps to help you.