Avast Security for Mac 70 hours still running

Imac 10,1 MACOS El Capitan ( 10.11 )

I downloaded and ran avast security for mac full system scan. It took like 48 hours to run the first time, identified 24 viruses / malware , half of which I moved to chest and when finished , i deleted the half in chest and the other half not in chest. I then ran the full system scan the second time. It already has taken 76 plus hours , has scanned 2223998 files identifying 11 malware / viruses and its like grinding to a halt. The full system involves a time machine backup disk . First time it took about 32 hours , scanned 2218730 files , identified 24 malware / viruses which apparently were successfully deleted. Now on this second run , it has detected 11 viruses/ malware which happen to be 11 of the 24 viruses previously identified and supposedly deleted.

So now its kind of turning to a bad jole where :

Apparently the malware/viruses were not deleted. The one common thing about not deleted items is that they are on a secondary login , not the one I am running on but the reports section does indicate that they were deleted. Do I have to login to the other user ID, run full system scan again and delete them that way?

right now its scanning jpg images on time machine disk and it roughly takes it about 10 minutes to scan a single .jpg file. what gives?

What will happen if I stop scan. Will I lose the identified viruses / malware or can I stop the scan and still remove the identified malware?

From what I read , slowness has to do somehow with time machine . Can I like just not scan the time machine?

On another note , I ran the security full system scan on another IMAC ( imac9,1 ELcapitan ) . it took much less time but it still took like 7 hours ( I think 500 gig or 1TB disk ). it identified dome malware / viruses , which were successfully deleted and a second full system scan took about same time and came up clean.

Do you have to reboot the machine after a scan is done and malware/viruses deleted?

DAzed and confused.

To get help, please post in the Mac section.
https://forum.avast.com/index.php?board=5.0