I'm very new to Photoshop I'm facing some problem in post-production.
I'm getting wired black spots while I'm working on the 32-bit channel. When I convert my 32bit to 16bit channel using a smart object I'm getting white spots in my image.
OK, from the comments I think I can see what you are trying to do. All those filters you are adding have basically destroyed the image. Try to keep the edit simpler.
Here's my suggestion:
Convert the rendered image into a Smart Object, and use the Camera RAW filter to darken the image by reducing the exposure and highlights, to make it like a night scene.
Copy and paste the original render on a layer above the adjusted Smart Object, and mask out everything except the areas you want to stay bright - i.e. the lit up parts of the building.
Here's an example