Ok, from what I can tell via Google’s translation, the arched gothic windows are finely cut plexiglass. They look beautiful!
In this post, there’s pictures of modern arched windows that fit snugly underneath 1×6 & 1×8 arches, and modern square windows.
But the most amazing part are the overhead 12V lighting plates! I’m thinking the lights are bright LEDs; hopefully they give off low heat. He has an example of the lighting plates illuminating the inside of a restaurant.