Thank you for answer. :)
I'm afraid I don't hear any volume reduction when I turn on the communcication setting. Youtube and games are still louder than the one I'm talking with.
Also I already adjusted the volume for each app. The thing is the program only shows up in the list when it's already producing sound, so that's already too late.
Except if I first turn the device volume down, then launch the app, turn down the app volume and turn up the device volume again for every single program I didn't launch before ofc. xd