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If your intended platform is a mobile device, it's pointless testing how it runs in the Unity Editor - a system which has many times more CPU, GPU, and RAM capacity - you need to be testing on the intended platform right from the start of your development.
I've already pointed out many common areas for performance improvement on mobiles, but to know which is causing the bottleneck for your particular game you need to profile.
Or, disable shadows, set mobile diffuse shaders on every material, static batch everything, decimate all your meshes by 50% at least, resize all your textures to 256x256 max and try it again. If it runs better, try re-enabling features one at a time until you reach the point at which you regard is acceptable performance.