If you wish, you can mute a single SMS conversation on the Oppo smartphone. We will then no longer receive any notification of new SMS messages. The mute can be unmuted in the same way as it is activated.

Android 10 | ColorOS 7.0
Step 1:  Open the  Messages -App
Step 2:  Open  Conversation  you want
Step 3:  Open the  Menu
Step 4:  Tap on  Mute notifications  /  Allow notifications
  1. Open the Messages-App
  2. Open Conversation you want
  3. Open the Menu
  4. Tap on Mute notificationsAllow notifications

Oppo Instructions