The most reliable way to obtain these games legally and safely is through official Sony channels.
You can purchase the original Universal Media Discs (UMDs) for the PSP from secondary markets like eBay or local game stores. Emulation on Mobile and PC Psp Games Download Full Version God Of War
If you no longer have access to a PSP, you can use emulators to play the full versions on modern devices. The most reliable way to obtain these games