The .rar extension indicates a compressed archive created with WinRAR. Because this is "part 1," you will typically need all subsequent parts (part 2, part 3, etc.) in the same folder to successfully extract the game.
For context on how games use infrastructure like GCP, official reports indicate:
The domain name compressedpc-com suggests a site specializing in "repacks" or highly compressed versions of PC games. While popular, these sites are often unofficial and can carry security risks such as malware or unwanted software bundled with the game files.