Oh do pay close attention while I grab on to your brain and twist your world around some .......Linux Mint (and all the Linux browser softwares when properly installed and kept current by installing their little green shield updates promptly) have very few handles for windows malwares to even try to attack and grab on to. Those little green shield updates cover the OS and all the free software you get from the Software Manager -- it is one cohesive update system.
And
It Isn't Windows so none of the things you used Avast for will even work on Linux Mint. It is naturally immune to them.
As a matter of fact, ALL COMMERCIAL LINUX ANTI-VIRUS products exist simply to protect the windows machines on your network that you may eventually interact with from getting a windows virus transmitted through a Linux machine somehow.
The Linux Kernel and the Mint distro itself has all the active Linux virus protections built into it and these are kept current by Linus and the maintainer boys --- skilled and dedicated folks who have a firm habit of completely eradicating any virus like stuff within mere days of it being discovered.
Something is found that can hurt a Linux machine, they immediately change the Linux kernel so that exploit simply cannot work any more ....... ever.So, you don't need to do Avast or anything else on Linux Mint.
You don't need to scan for malware every few months. I had installed Clam AV on my machine (FOSS software from the Software Manager) just to protect other users running windows machines, but I really don't need an antivirus on my Mint machine at all. Clam AV didn't require me to do scans or anything else, it just dropped a mini window a few times to say what it had just killed and they were all Windows Natural illnesses that could not have hurt me on Linux Mint anyway.
You don't need to defragment or compress or "clean up your hard drive" again, ever. Your hard drive's formatting will be changed during the "take over the entire hard drive" installation to a Linux hard drive format that does not get clogged up or slow down, ever.
It is a self-correcting format and it never needs attention paid to it ever again.
Your Linux operating system does not get old or slow down over time, it does not degrade at all during the period of time between major upgrades.
Linux upgrades do not cause problems nor do they require "more resources" -- the opposite is true as Linux speed improvements over time are the rule of thumb, not the windows like long term performance decay you are used to seeing.
==================================================
I actually felt plumb LAZY when I first went to Linux Mint because I didn't have to spend time doing routine "proper machine maintenance" all the time like I had to do on Windows.
And I can vouch that Linux Mint machines really don't slow down or get crapped up over the years like a Windows machine.
And no, you won't really believe it either, until about 5 years or so have gone by ......
Here are a couple of websites that list all the Linux viruses "found in the wild". Please note the end date on many of them as that is when the kernel was fixed so they simply cannot be any more. Also note that some are internet based viruses that exist on the web or on Windows machines and can be re-transmitted endlessly, but do not really affect Linux machines any longer since kernel fixes were put in place.
https://www.unixmen.com/meet-linux-viruses/https://en.wikipedia.org/wiki/Linux_malware#Viruses