Parts of my mesh aren't rendering and do other goofy things

I am very new to Unity so if you would please dumb down your answer for me that would be appreciated.

I have a high poly model made in maya and when I play the scene most of the scene renders fine but a few meshes don’t render at all, some are half invisible and flash when you move around the screen and other pieces kind of spin as you walk around them.
I have tried deleting all the objets history and non-deformer history in Maya but all it did was remove some lag in the game, not fix the mesh issues.

How do I fix these problems? The end ‘game’ is simply you can walk around in the scene, nothing complicated but I just need to know how to fix the scene?

Thank you for your time.

Sounds like you have some normals inverted on your meshes. Try fix it on Maya, or change the to Calculate Normals on the imported mesh on Unity.