I improved your PG a bit - https://playground.babylonjs.com/#8LFTCH#1016
What I can say:
- The model is too big (128 Mb). I believe that such a model shouldn’t weight more than 20 Mb if you aim to real time render.
- GTLF doesn’t support environment export, so you need to create this in Babylon.
- There are a lot of conflicting planes. I fixed the floor (which doesn’'t blink anymore) but are you sure that you’ll need the outer floor to be shown to somebody? If not, just delete it.
- Here are a couple of helpful links: What are the best practices for environment meshes made for Babylon? and Optimizing scenes for better WebGL performance - Soft8Soft . Hope it may help