Here’s a clear, step-by-step content draft on how to open Fastboot Mode on an Oppo A37.

This is the standard way to enter Fastboot mode directly from the device. : Completely turn off your by holding the button and selecting "Power Off." : Once the phone is off, press and hold the buttons simultaneously for several seconds.

Prerequisites:

Wait for Reboot: Your device will automatically restart into Fastboot mode. Exiting Fastboot Mode

If you can reach Recovery Mode, you can often jump to Fastboot from there.

Release Buttons: Let go of both keys as soon as the Fastboot Mode screen appears. Method 2: Using ADB Command (Computer Required)