Silent Mode?

When do I set silent mode so those popups don’t appear when I’m scanning?

What messages? Above the system tray?
It seems that you’ve changed the avast settings without knowing what you were doing…
This is an option disabled by default. You can turn it off going to the Standard Shield provider settings, Advanced tab an unchecking ‘Show detailed information on action performed’. You can do this for the other providers too.

Welcome to avast. The most configurable antivirus around 8)