How to remover yahoo search from safari

Go to Safari in menu bar>settings>search and see if google is set as search engine

If this is correct, maybe yahoo is set as your homepage. Go to Safari in menu bar again, settings General> homepage and check if your homepage is not yahoo. If it is yahoo, you can change it to anything you want

Google as the search engine is the default choice, but is not the 'correct 'choice.

I use DuckDuckGo and it seems to offers far less tracking.