Best approach to change your search engine to google?

Depends on the browser. Chrome: Settings > Search engine, pick Google from the dropdown. Edge: Settings > Privacy, search and services, scroll right down to Address bar and search. Firefox: Settings > Search, default search engine. If it keeps flipping back to some Yahoo or random search page after you change it, that's almost always an extension or a bundled program doing it. Remove anything in the extensions list you don't recognise and check installed programs for something you didn't mean to install.