[Zubersoft]

You can just turn down the system volume with the volume buttons on the device itself. MobileSheets can adjust the system volume up or down, but this is going to apply to all applications - it can't mute external applications while generating sound itself, for example. As far as notifications, you have to disable notifications in the OS settings for each app. That's not something MobileSheets can control, as it's something the operating system manages. Some devices may also have a "Do not disturb" type mode which should disable notification popups. I would recommend going through each app in the OS settings and just turning all their notifications off.

Mike