Hi,
https://www.openstreetmap.org/way/1275471505 looks like a building but it is not tagged like a building and therefore not rendered like a building. (seems to be a common mistake in your area). If the building is for indoor horseback riding you may use https://wiki.openstreetmap.org/wiki/Tag:building=riding_hall.. If the whole farm is larger than this building, it is better to map the farm as a separate object, compare https://wiki.openstreetmap.org/wiki/Tag:leisure%3Dhorse_riding, example https://www.openstreetmap.org/way/486850438