Hi you have a missing texture in your map all over the ground in version _a3b:
You can pack custom textures into your map using packing software like
Compilepal. Currently valve's built in packer bspzip doesn't work.
You can check if any assets (models, textures, sounds, particles, etc) are missing by, before loading the map, going into console and typing:
This will tell TF2 to load the next map with only the assets that are in the game files or that are packed into the map file, showing any missing files in this ugly purple.
You also have a lot of empty space on this map and sightlines:
You will get better at map scale as you play the game and distinctly observe map scales. For now try to think about mock gameplay scenarios in your map and how you'd solve them, and if you need to add any platforms, walls, or just filler objects (like massive blocks of geometry, try not to fill with props!) then try to do so.
At the moment you should try to make players not have to 'just hold W' to get through the map - if players have to jump on things or over things or walk around things it's more interesting and fun!
Hope to see more!