How to disable Andriod message+ notification sound while using the app

[Android Central Question]

I get a notification that I received a text message in message+ from a friend. 😎
I open it. As I'm trying to reply to her message. She's already texted me 15 more times. All I can concentrate on is that annoying tone. Well, it use to be my favorite 😔How do you disable the sound notification while texting the same person