I think I am in a similar situation.
https://forum.avast.com/index.php?topic=191288.0For the past few weeks I have been getting messages from Avast at random times saying "Firewall Mode Changed. We detected the network BT Public Internet Service and automatically changed the Firewall Mode to Private/Low Risk mode".
I really don't know what that means, why it has changed the 'mode' - whatever that is, or what the significance of these messages is.
Avast keeps generating new profiles, public and private, for me, even after I've deleted the ones I don't think I want. Someone here told me to do this, but I have to say that I don't really understand what I'm doing. The profiles refer to MAC addresses, but these don't look familiar and I don't know how to find out what they correspond to.
Ideally I would rather not get these messages, but having got them I would like to reassure myself that Avast is really doing what I have paid it to do, so, reluctantly, at the tender age of 73, it looks like I'm just going to have to find some time to learn how computers and firewalls work so that I can understand these new messages and the replies I get from the helpful experts on this forum.