You can absolutely extend internet access from one building to the other. When configured properly, Ubiquiti NanoStations or NanoBeams are effectively a layer 2 bridge, so you can extend subnets / VLANs across the link.
One option would be to do two point to point links on different frequencies, with two radios on the upper left building and one each on the buildings on the right side of the map. Alternately, you could put one radio on the upper left building, configured as an AP, and hit it from radios on each of the other two buildings. In this way, your capacity is diminished because both of the other buildings are sharing bandwidth; that may or may not be a problem depending on what performance you need.
On that note, what kind of performance are you looking for, and in terms of communication between the physical spaces, which buildings will be communicating with which other ones at what desired capacity? Knowing that, it's then possible to get into more specifics.