My game has a very Low fps (about 8-10) fps when i look straight ,,, Both in editor and mobile,,,

I have a scene where i have some buildings made by simple cubes, Tris and verts count is high and is more than 3-5m, when i look towards high tris and verts direction i get a 8-9 fps, 119433-disabled.jpg , Please help me with that i am working on my final year project and i cant show a game that has a very low fps

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Do you have a coroutine using a loop out of control?
Also, 5millions of polys are too much, i try to work to not more than 1million, and that is if its just a walk, anymore complicated can block everything.

You tried occlusion culling? That is one of a lots of ways to optimiz you game.
Also you can use normal maps or heightmaps instead of use a high-polygon 3D model.