|Any (System) Restore points for a date prior to the problem arriving?|
And yes you dun the right thing by hanging up on calls saying you have a problem and "we" can fix it... Very much sounds like a Scam...
Possibly you might uninstall Avira and see it the resolves the problems? If it does. then use a freebie anti-virus utility in its place; and there are several recommended here. Bitdefender, Avast, AVG, Sophos to name a few.
I'd wait a wee while for others to drop in and perhaps offer a few suggestions beside the System Restore point I've mentioned above.
Failing which... no System Restore points available... - go to tweaking.com
and download/run their utility "tweaking.com". The actual download is via a (linked) "mirror" site. This utility will go through your windows installation and fix anything it find that's not as it ought to be. Be careful NOT to download/run a registry repair item, and/or other utilities which are all too easily downloaded by mistake.