If you want to play the authentic game on your mobile device, you should use official cloud streaming services rather than searching for ISO downloads:
Indie developers sometimes create small-scale racing games for Android that use FH5 assets. How to Play Forza Horizon 5 on Android (The Real Methods) forza horizon 5 ppsspp iso download android mobile new
To be direct: Forza Horizon 5 cannot be played as a PPSSPP ISO file because it was never released for the PlayStation Portable (PSP) If you want to play the authentic game