Forza Horizon 5 does not exist on the PSP (PlayStation Portable). The PSP was discontinued in 2014. Its hardware maxed out at 333MHz CPU and 64MB of RAM. Forza Horizon 5 requires a modern PC or an Xbox Series X|S with ray tracing, massive polygons, and advanced shaders.
PPSSPP is a PSP emulator. It can only play games that were released for the Sony PlayStation Portable. Since Forza Horizon 5 was never released for the PSP, there is no legal ISO file for it. Forza Horizon 5 does not exist on the
For advanced users: Winlator (a Windows emulator for ARM Android) can run Forza Horizon 1 (2012) at 15-20 FPS on a Snapdragon 8 Gen 2. It cannot run Forza Horizon 5. Anyone claiming otherwise is lying. No Textures / Weird Cars: