The good news is in a big game like yours I think you can improve your fps easily.
What I learn from the different documentation I have been reading is geometry, lighting and code can have a big weight in performance. I see in your stats you have 3.3M of tris, 2032 passes, 609 shadow casters and 2809 batches.
I think one of first things you can try and it’s really easy, it’s the Occlusion Culling, so instead of rendering the whole level, the camera only renders what sees, that should drop your tris, passes, batches, etc. and improve your performance. Here is some info: https://docs.unity3d.com/Manual/OcclusionCulling.html
For the shadow casters, check if you really need those elements to cast shadows. Sometimes the element is already in a dark area and the shadow is not noticeable. And bake your lights, I don’t know how many lights you have, but I feel with one or two directional lights, and baking the rest you will get similar results.
For your code another big improvement is only use update if you really need it, you can mostly replace the update by using coroutines.
Those are just some of the general things you can do, I feel optimizing is the sum of lots of little things. If you are interested in optimizing I highly recommend these collection of articles, they were really helpful for me:
Hope it helps