Hi @prachi_ch, I have Samsung Odyssey headset so I do not know how to upload the scene in oculus Quest. I supose the oculus Quest have a limit managing large scenes because is not supported by the PC, it is a stand alone headset.
Can you share your scene to see what we can do to help you?
Stair case: Shapespark releases - #54 by jan
Performance and quality: remember the difference beetwen resolution in headsets and others devises, HP Reverb have the Best resolution in headsets, look this table to compare
List of virtual reality headsets - Wikipedia
Every headset have less quality compares with cellphone or pc screens