The Oppo A37fw is a 2016 entry-level device (MT6750, 2GB RAM, 16GB storage). Official support ended at Android 5.1 (ColorOS 3.0). Custom ROMs are scarce but exist mainly on Chinese forums (like NeedROM, 4PDA, XDA-Developers — though XDA has limited official threads).
: This ROM is a favorite for users who want high levels of customization, offering a polished experience that balances stability with a feature-rich interface. AOSP-based ROMs Oppo A37fw Custom Rom
Flashing a custom ROM is a technical process that and carries a risk of "bricking" (rendering unusable) your device. The Oppo A37fw is a 2016 entry-level device