Performance Problems when too many objects on screen

I hope this is the right category for this question

Using UE5.3
I have a 3d game enviroment

With this building. The game is made for supposedly low end devices.

Problem:


When the player is in a position, where, as here shown in the image, the player looks out of the window into this middle of the building, everything is loaded, causing FPS drops from constant 60 to 20ish.

First Question/Help
If someone would perhaps know a technique or anything relating to performance optimization in such situation or level design whise, I would be very glad for such help, literally anything^^

Have already tried:

  • using cubemaps in front of windows(looks bad and also I cant have a million diff cubemaps for all the different angles in the game, and having it update in realtime is too ressource intense)
  • Also tried to figure out what exactly causes the lag by using Unreal Insights, though the machine I am testing on doesnt have any performance problems, and the low end devices I am targeting are not able to run unreal engine so

Second Question/Help
Are there other ways of figuring out what causes the bottleneck in such situation?

If I can provide any additional helpful information, please tell me :smiley: