Open In Progress FPS Drop: Mount & Blade Warband

[Gozzillas]

Hey guys I'm here looking for help because since some weeks my Napoleonic Wars game had a huge fps drop without any reason. I used to play it with 60 fps stable. May you know the reason or do you know how may I solve this?
I already tried with updating video card drivers and uninstalling game and re-installing it.
8GB RAM
Gtx 1050 Ti
i5 4460 3.2 GHz

Edit: No process on background when I play Mount and blade

 

[MArdA TaleWorlds]

Have you installed any modification or change anything game or GPU related?

 

[Gozzillas]

I have not

 

[MArdA TaleWorlds]

Do you remember the particular environment when the FPS drops happen? Or the game is always laggy?

 

[Gozzillas]

Yeah, If I play alone with some bot on a little sized map it does not lag very much.
The game starts to go under 20 FPS if I play with 20+ players on a large map.
As I already said several weeks ago I did not have this problems, so I don't know the reason...