On the Oppo-Smartphone you can delete single or multiple SMS messages, and by tapping and holding a message a pop-up window opens where you can start the deletion process.
Deleting multiple messages from a conversation is a bit cumbersome. After tapping and holding a message, you have to select "More" in the pop-up window. This opens the edit mode for the whole chat. By selecting multiple messages you can delete several messages at once.
- Open the Messages-App
- Open Conversation you want
- Tap and hold the Message you want
- Tap on Delete