If you are using the legitimate streaming methods, the process is straightforward:
The base game of GTA 5 on PC/Console is over (including textures for Los Santos, Blaine County, radio stations, and 4K assets). No current smartphone has a standard OBB partition large enough to hold that data. The Android OBB folder typically caps at 2GB to 10GB per app. You cannot fit a 100GB game into a 2GB OBB file. gta 5 android obb data download link
If you decide to download GTA 5 for Android from third-party sources, ensure they are reputable to avoid malware. If you are using the legitimate streaming methods,