Judging from the screenshots, the map is like super open and big. Notice all of the unnecessary, open space in the top left corner of the red triangle (or top right corner of the blue rectangle) in the overview screenshot. Compile the map and run around it as a pyro, soldier, or engineer as they have basic speeds, and get a sense of scale. But don't make the map too small as you want to have enough space for all of the players.