Like Dave, I had a look at your file. He’s got you sorted as far as revealing the hidden objects in your room.
But I don’t understand quite why the file size, even of the room alone, is so big - over 60MB with materials applied, and even deleting all the materials leaves just over 40MB in the file.
I had a look with Steve Baumgartner’s Statistics Probe. The cupboard with toy animals accounts for 140,000 edges, and the chair about 51,000.
Take care when importing models from the 3D warehouse (if that is where you got them from) to avoid over-detailed models - they will quickly slow down your modelling.
Check each imported model in a new file, and reject ones with either large edge counts (see Model Info/Statistics) or large file sizes.
If the material texture sizes are large, they too will bloat your file.
I suspect both have contributed to the excessive file size and edge count in your model for the level of detail you actually need.
As Dave said, there are still a lot of reversed faces in your model - it’s easier to see them if you view your model in View/Face Style/Monochrome.