Drastic FPS drop after importing a model from 3Ds Max

Hello, guys. I've a little problem here.
I've got an assignment to recreate not so large house in the 3ds max and port it to Unity.
Probably I've made a mistake importing all furniture and so forth stuff in 3ds max first, not in Unity after importing there just walls and doors. Because I think it's a main optimization problem, 3ds max tries to save all vertices and faces...

So after exporting to Unity, I've got insanely lagging edit and play modes. It's around 2-5 fps (only if you look at the house, but at other directions I got clear 60 fps). I added some lights, checked the profiler, it showed around 7M vertices and tris, but with light it can jump up to 20-30M. I know it's not normal.

I've tried to fix it somehow (actually I just need to add some scripts and triggers to pass this work, but with this kind of lags I barely can edit anything). I went to 3ds max and checked polycount, it says 3.4M tris. It's a lot I think, but mostly it's come from other imported models in 3ds max (like furniture, chandeliers and so on).

I've used Batch Optimization and got 715k tris (not so bad) but model became awful, with a lots of holes in imported ones. I imported it to Unity and thought it should work smoothly, but in reality I've got almost the same thing, but now turned on lights affect performance. It's like 20 fps without lights and 2-5 fps with them (I set them to baked mode, but nothing has changed). I checked the profiler, result without lights are kind of reasonable: 1-3M tris (almost like 3ds max polycount number) ((ref. profiler picture at the end of the record), but with lights on I am getting 16M tris and 25M vertices (ref. profiler picture on the start of the record).

What can I do to improve situation (or just to finish my task)? Should I furnish with models in 3ds max or in Unity after importing basic walls? (I asked classmates who built a level (house) in Unity they're having no problem at all).

P.S. PC: i3 (3.2GHz), 4Gb RAM, GT730 (2Gb). Unity 2019.3, 3Ds Max 2020.

 

i can see that you have a lot of drawcalls.
Depending on what renderpipline you use there sre different things you can do to batch those drawcalls together.
In the defalut reneder pipline you can mark all objects that can not move as batching static.
In HDRP or URP there is a option called SRP batcher that will reduce the drawcalls by alot.
Another good tool for optimisation is occlusion culling.
This will prevent unity from rendering objects that are hidden by stuff like walls or the floor.

 

@Radmir2015
Di's you figure out what was causing this weird problem?