Not sure how I can help you. When I first installed Avast, every website on Chrome, including all the major search engines was blocked with an Avast "Your connection is not secure" message. I see others have had this problem. Ironically, mine was on Chrome, not Firefox. I figured that the default blocking criteria was set so broadly, that I'd have to go back in and tailor it. Some of the terminology in the settings was not clear. More reading and visiting other forums.
The email problem was puzzling, and not sure how to deal with that.
Bottom line is that I have a business to run and can't spend a lot of time to sort out a program that I've done fine without for years.
I can't afford to not have a client receive a file properly the first time I send it.
I keep good practices and a periodic file scan should do me fine, since all my viruses came in unopened spam emails.