The brightness of the Oppo smartphone's screen can be adjusted automatically or manually, using the display settings and the quick settings, which include a slider to change the brightness manually.

Android 10 | ColorOS 7.0
Step 1:  Open the  Settings
Step 2:  Tap on  Display & brightness
Step 3:  Move  Slider  to adjust brightness
  1. Open the Settings
  2. Tap on Display & brightness
  3. Move Slider to adjust brightness

Oppo Instructions