search.yahoo.com redirect

Hi,

I have a MacBook Pro 2012 with a 2.5 Ghz i5 processor, 4GB memory, OS X El Capitan version 10.11.6 and I recently downloaded something off the internet by accident (sadly a popup that I did not intend to download) and realized that it had some sort of malware. My laptop has become slower and every time I search something in the search bar, it redirects to search.yahoo.com even though my default search engine is Google. I've already deleted any apps that are unfamiliar to me, checked and removed any extensions that I do not recognize, and reset settings in Google Chrome and Safari, but none of it has solved the problem. Are there any reliable apps I can download to solve the problem? If I bring my laptop to the Apple Store, would they be able to help with my issue?

Thanks in advance.