The fundamentals for this type of app can be found at https://doc.babylonjs.com/babylon101/cameras,_mesh_collisions_and_gravity. In the example playground on this page use mouse to look around and cursor keys to move. (Click on scene before using keys)
In the app you posted, like the crate in the example on the above page, the stands are just boxes with different materials applied and walls are formed in the same way. You can apply material with transparency for the windows and use a skybox for the outside view.
For links to ‘stand business’ add an event to each box representing the sign.