Safe finder

In Safari > Preferences > General > Homepage ensure it's set to something you're happy with (such as google.com).

Close the Preferences window.

Reopen the Preferences window.

If the home page has reverted back to Yahoo Safe Search, download and run the free version of MalwareBytes.

Then report back!

I'd suggest downloading and running Malwarebytes. It's free to run and you can delete it once you're done.

https://www.malwarebytes.com/mwb-download/

Make sure you only download it from the Malwarebytes website.

If necessary, follow the manual instructions.  Do not download any other programs that are listed in the articles.  

See if the below helps. I would scroll down to the below or you might fall asleep.

Step 1. Eliminate Yahoo Redirect from Windows.    

Step 2. Delete Yahoo Redirect from Mac OS      

Step 3. Uninstall Yahoo Redirect from Internet Explorer      

Step 4. Remove Yahoo Redirect from Microsoft Edge.     

Step 5. Erase Yahoo Redirect from Mozilla Firefox.   

Step 6. Get rid of Yahoo Redirect from Google Chrome.    

Step 7. Eliminate Yahoo Redirect from Safari.   

https://www.2-spyware.com/remove-yahoo-redirect-virus.html.    

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.

Safe Finder Uninstall

Safe Finder Uninstall (2)

Safe Finder Uninstall (3)