Yahoo is taking over google on safari? How to fix this?

   1. Remove adware installed on your Mac..

       Run the latest release of Malwarebytes for Mac to remove malware/adware, if installed on your Mac.

       For instructions: Install Malwarebytes for Mac v4      Uninstall Malwarebytes for Mac

       Click the “FREE DOWNLOAD” button.

       Click the “Scan ” button. Once done, quit Malwarebytes for Mac.

       Restart the computer and relaunch Safari holding the shift key down.

       Scan for Malware again.

       Additional steps  if necessary.

  2. Reset search engine:    https://support.apple.com/guide/safari/customize-your-search-ibrwe75c2a3c/mac

  3. Reset  Homepage.   https://support.apple.com/guide/safari/set-your-homepage-ibrw1020/mac 

Also go to Safari Preferences/Extensions, uninstall any you don't recognize, and then turn all extensions off. Test. If okay, turn the extensions on one by one until you figure out what extension is causing the problem.

 Safari/Preferences/General - see what the Home Page is set to. If something you don't recognize, see if you can replace it with something you want.

 Safari menu/Clear History.

 System Preferences and remove any Profiles you see.

If indeed MacBooks do not need antivirus how are apple not monitoring these pages to see the difficulties that malware is causing users as well as other issues? I for one do not understand what is a suspicious site by looking. More needs done to assist users using their MacBook .My google page is being hyjacked by yahoo every time I go into it.This issue is giving me grief and I find it difficult to trust the fixes as these could be putting my MacBook in a worse scenario than before. I did buy apple support when I bought my mac but that was a good few years ago. I am now more aware and confident if given clear and precise instructions to eradicate issues but who do I trust?. I have no issues using my android phone but find apple could do a lot more to help people who have spent their hard earned money.

I would follow dominic's suggestion to use Malwarebytes. The program was written by Thomas R, a long time poster.