RTF is a global modification that replaces all towns in the game.

There are a lot of polygons; the game engine simply isn't designed to handle that many in a single mesh, plus the triangle normals... in general, you just need to reduce the number of triangles!

What's wrong with the triangle normals? Where did you get that information about the number of polygons? I didn't make the model with 1,000,000 polygons; it has about 7,000, right? And I sent test screenshots; I didn't change the number of triangles, so why are there fewer holes?

And finally, it's not possible to easily reduce the number of polygons without distorting the model. All these modifiers either work on simpler surfaces or with a small percentage. So, instead of 7,000, it will be 6,500. Is that optimization?