If you are being redirected to a different search engine other than the one you have specified in your browser, there could be several reasons.

When you installed a program, it might have given you an option to do a 'full install'.  Sometimes this actually means it's installing a suite of programs and may include modifying your browser's settings or adding an extension to your browser.

But if you are getting a different search engine in all your devices, including your phones, it probably means your ISP has setup your router to use their DNS services. Problem is that some ISPs direct your searches to their partners.  That gives them revenue for each search completed.

To prevent this, you can setup your router to use 'open' DNS servers that do not modify your searches. This video covers the methods to setup your system to use OpenDNS.