How to get rid of a computer virus that directs the search on google to an advertising website?

When I try to search something, the website is replaced with many different kinds of an advertising sort of sites and sometimes comes up with freescan.antivirus.com. So, when I click on the site, it directs me to a weird site that has nothing to do with what I’m trying to search for. I’ve downloaded many anti-virus and malware softwares, but they aren’t helping.
When I try to search something, the website is replaced with many different kinds of an advertising sort of sites and sometimes comes up with freescan.antivirus.com. So, when I click on the site, it directs me to a weird site that has nothing to do with what I’m trying to search for. I’ve downloaded many anti-virus and malware softwares, but they aren’t helping. I’ve now tried Malwarebyte, spybot, AVG.. still not working.