Searching for "GTA 5 highly compressed 500MB" usually leads to one of two things: a file that won't extract because it’s corrupted, or a "fix" for a version that doesn't actually work.
The smallest stable version of GTA V is the FitGirl Repack, which compresses the 72GB game down to 35GB (or as low as 22GB if you exclude Spanish/French audio and 4K textures).
Downloading and Installing a Working GTA 5 Version
Let’s be clear on the technical limitations. The original GTA V contains:
Direct Answer: A legitimate 500MB "highly compressed" version of for PC does not exist. Grand Theft Auto V requires at least 72GB to 105GB