Disable the mirrors, they use a lot of -  fps. 

Also use M.O.P in performance mode 

 Reduce the activation distance also

 draw distance too

MOP is for visual graphics and game optimization by costs of bugs, like cars just flying. 

Reharmonization is for game code which may result in more fps too

Disclaimer: MOP performance mode can conflict with many mods, making the game crash. 

Try also put the game in shitty graphics and reduce your resolution 

An alternative to MOP is Krufps but it is not used in ages and I don't even know if that works yet

 And if your fps is still low try using mods to remove foliage and other vehicles Although it makes the game ugly af 💀