Almost never. Repacks are typically created for the single-player story mode and have all online functionalities removed. To play GTA Online, you must have a legally purchased copy of the game.
Downloading a repack of GTA 5 is an act of software piracy. While the immediate concern for many is the malware risk, it is important to be aware that distributing and downloading copyrighted material without permission is illegal in many jurisdictions. Download Gta 5 Highly Compressed For Pc In Parts
Before downloading GTA 5, ensure your PC meets the minimum system requirements: Almost never