Ok, time for real detailed criticism rather than "its empty"
The main problem with your build is the lack of cover. The overall design would work fine if there were more consideration in constructing props like half-buried pipe sections or large horizontal fuel tanks, and a better terrain than what exists now. You also provided too much excess space in the building without filling it up; its not as if warehouses are 100% empty. Putting some walkways through there (more than just the one next to the window) would work well in breaking up the unused space.
The tunnels that you "walk through" are pretty much deathtraps; they're excessively long and offer no space to duck behind cover. Even though real tunnels are like that, they're rarely that long and have a sharp turn.
The main courtyard/space has practically no cover. This also goes for the buildings that you show. Trees offer little-to-none protection due to the tree trunk being so small, so you should scatter boxes, debris, etc there. Put a little more effort into constructing duplicated props that you can use around the whole build.
