Everyone understands that the model is just hacked together. I think of it like pieces of cardboard cut out freehand, in the old days.
So don't worry about it.
A good composition is compelling regardless of the model completeness.
You should download the student version of Artlantis Studio to get better renderings. Artlantis has automatic sky.
Otherwise, use a photo background from the Archicad library.
To add light color to the sun, study the sun dialog accessed through the Perspective Setting dialog or the Camera dialog.
To make glass clearer, study the material settings for glass and find out.
Dwight Atkinson