The developers abandoned these ports years ago. You cannot fix the broken camera without compiling your own kernel (nearly impossible for MediaTek).
: The Oppo F1s officially stopped receiving major updates at Android 6.0 (Marshmallow). Any MIUI 8 build is an unofficial port . miui 8 oppo f1s
: Download a compatible MIUI 8 port for the Oppo F1s (often based on Android 6.0) and save it to your internal storage or an external SD card. How to Install MIUI 8 on Oppo F1s The developers abandoned these ports years ago
were considered experimental. Users often reported bugs with the fingerprint scanner camera stability battery calibration miui 8 oppo f1s
: Save the .zip file to your device's internal storage or an external SD card.