These versions, like the "Optigos" mod, achieve extreme sizes by removing up to 98% of game content . You lose missions, audio, radio stations, most textures, and the entire GTA Online mode .
Rockstar Games does not authorize repacks. Downloading a cracked highly compressed setup is piracy. If you love the game and can afford it (it frequently goes on sale for $15), buy the official version to support the developers. Gta 5 Highly Compressed Setup For Pc