The first floor is 600 square meters. If it is not blocked, it is easy to do, 200 m optical fiber, one enterprise gigabit route and one AC. Gigabit switch. Two small APS or one big AP on each floor will do. This should be the most economical and convenient solution.
Incoming and routing switches are on the fourth floor. Three lines up, three lines down.
If there is a dead angle, add an AP.