reducing polygon and vertices counts in video game assets like guns to maps etc in ue4 games

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I Was Wondering If This Could Be Done In Games Like Star Wars Jedi Fallen Order On PC To reduce the amount of vertices being rendered to increase performance on lower end hardware and increase fps

i was ideally hoping to take the game files reduce them to workable formats like stl files then open them up in blender as that is the only modeling program i know how to properly use and then simply reduce the detail, then wrap up the stl files and put them back in the game just like at the beginning only now it should have a bit less detail and run slightly better,

TLDR In Other Words I Want To Optimize Games On The Unreal Engine 4 By Removing Small Unnoticeable Details On A Large Scale Hoping To Increase FPS When Playing The Games.

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Any Replies With Any Knowledge Would Be Very Helpful As Apart From This very Simple Imagining Of How It Would Happen I Have Zero Clue On What To Do.