What was the goal? To recreate the scene in 3D with the identical perspective? Do you want to recreate the look and feel of the Image too? If yes, increase the roughness of the window construction and add more blue to the lighting. Did you use light probes?
Well, thank you for the critics.
Generally the goal was/is to start/excercise recreating scene from an real image.
What should I work out /in steps?/ to improve the result w/out crazy, time consuming modelling?
Your’re welcome. Try to recreate the lighting and edit some shaders. Did you used light probes? I would use Reflection Plane Probes for the glass and the floor, a Cubemap for the glass sculpture and an Irridiance Cache for GI. For lighting use a blue sky to get the blueish tone. The image of a city is a Image Plane with a Emission shader. To get nice shadows and a bit of yellowish color, use a Sun Light.