The Octan Office is a Lego MOC created by Łukasz Libuszewski. This Modular style building uses 2,542 pieces. The office is actually an alternate build of the Corner Garage (10264) Modular Building. It uses about 90% of the pieces from the original, and 240 or so pieces have been added. The ground floor features the Octan office and an automotive parts store. A small pet clinic takes up the second floor, and a small apartment gets the third floor all to itself. This Lego build features a lovely roof line, with some very steep slopes and sweeping curves. Besides the three modular floors, the back features two huge window sections that can be removed for easier access. If you find your Modular City has too many corner buildings, it may be time to try an alternate Corner Garage.
The designer of the Octan Office has drafted up a set of instructions, which goes over the 2,303 pieces conversion of the Corner Garage, and the 240 that you will need to add. That manual can be found for sale over here, and you can find more details, and more photos of the finished build: https://brickative.shoplo.com/category/modulars/octan-office