There are indeed two staircases that lead to platform B but I'm not sure if they are located as shown on the 3D map though. The eastern one is at 45 degrees, the other one should be at 90 degrees. If I remember correctly, both of them are on the west side of the fountain.

If you can, take note of where https://www.openstreetmap.org/way/895638677 actually starts. If I remember correctly it should be between the stairs from the square and the fountain.

The path that goes through the middle of the fountain should go around the south side for sure.