WLAN connections can be removed on the Oppo smartphone as quickly as they have been added, and there are two ways to do this under Oppo's ColorOS

If there is an active connection, just tap the WLAN network and then tap "Remove this network".

If there is no connection or if several WLAN connections are to be removed at the same time, several connections can be deleted simultaneously in the Advanced Settings.

Android 10 | ColorOS 7.0
Step 1:  Open the  Settings
Step 2:  Tap on  Wi-Fi
Step 3:  Tap on  Advanced settings
Step 4:  Tap on  Saved networks
Step 5:  Open the  Menu
Step 6:  Tap on  Edit
Step 7:  Choose desired  Connection
Step 8:  Tap on  Remove
Step 9:  Confirm with  Remove X Network(s)
  1. Open the Settings
  2. Tap on Wi-Fi
  3. Tap on Advanced settings
  4. Tap on Saved networks
  5. Open the Menu
  6. Tap on Edit
  7. Choose desired Connection
  8. Tap on Remove
  9. Confirm with Remove X Network(s)

Oppo Instructions