Run a scan with AdwCleaner, as malware can often change your default search engine:
https://www.malwarebytes.com/adwcleaner/
(Simply download it and run the file. There's no installation process).
However it's not clear to me exactly where you're encountering Google. Is it appearing as your browser's home page or are you getting results from Google when you use the search box (or address bar) at the top of your browser window? (Changing your default search engine won't change what appears as your home page and, of course vice versa).
It would also help to know which browser you're using, so that we can provide you with instructions specific to that browser.