Avast is an antivirus that can't detect virus

Ok so , this started when i start wondering WHY i never get infected altough i installed hundreds of free software from internet , everybody should know free software from internet is a clean path for viruses to reach your computer.

So i updated the virus definition to the latest , did a full scan , did a boot scan , and avast says my computer is clean.

Then from searching i found the best SECONDARY antivirus in my country called SM**** (I know im not allowed to publish the name in this forum so i censor it) , did a full scan with it , and found 7 viruses !

How can avast as a PRIMARY antivirus that work as defenders in the front line can’t detect virus that SECONDARY antivirus can detect .

After 3 year with avast , i’m disappointed now , please explain avast , you just made my computer VULNERABLE for 3 years straight because of the false warning saying “your computer is safe” after did a full scan with avast.

https://i.ibb.co/4Z9FW2Y/IMG-20200331-083513.jpg

How do you know detection is correct and not false positives ?

No security program have 100% detection or zero false positives

After 3 year with avast , i'm disappointed now , please explain avast , you just made my computer VULNERABLE for 3 years straight because of the false warning saying "your computer is safe" after did a full scan with avast.
Have those files been on your computer for 3 years?

@pondus i can send you the infected file if you want , and these file that detected as virus is one of the recent free software i downloaded from internet

You can upload and test file(s) here www.virustotal.com

post link to scan result(s) here