hey and welcome to the forum. avast smart scan does not delete files that is linked to a browser, but it could be related to grimefighter but makes no seens either.
also you should not have to make an exepction in avast to install opera either.
small suggestion lets have a expert have look just in case
please follow this guide and attach the basic logs from mbam and frst+addation
https://forum.avast.com/index.php?topic=53253.0
good luck
