I got this message: Your Mac is heavily damaged! (33.2%)

It's a scam. You have no virus. You might have equivalent problems were you to actually download it.

AMC's own removal instructions - http://advancedmaccleaner.com/uninstallguidelines

Feb 2018 Apple Support Communities discussions on removing AMC:

https://discussions.apple.com/thread/8297821?answerId=33081952022#33081952022

https://discussions.apple.com/thread/8226795

How to block pop-ups in Safari - Apple Support - https://support.apple.com/en-us/HT203987 - "Learn how to block annoying pop-up ads on your iPhone, iPad, iPod touch, or Mac."

Feb 2017 macjack post on dealing with Safari virus warnings [on Mac] - https://discussions.apple.com/thread/7867552?answerId=31415398022#31415398022

April 2018 VikingOSX post - https://discussions.apple.com/thread/8350243?answerId=33262151022#33262151022

A Browser Pop-up Scam has Taken Over Safari - https://sites.google.com/site/appleclubfhs/support/advice-and-articles/browser-p opup-hijack-safari

You may see this just by visiting a normal web page. Closing the page might be enough. The warning may appear real but realize your browser provides a certain amount of information about your computer configuration to any web site it visits so the site can customize the page to fit your browser, but then bad sites can make messages appear "personal".

You don't need to do anything other than close the scam page. There's nothing wrong with your Mac.