You have adware/malware installed. Use Malwarebytes Anti-Malware for Mac. It may be necessary to run more than one scan. After scanning a couple of times, restart the computer and test. If necessary, follow the manual instructions. Do not download any other programs that are listed in the articles. Malwarebytes uninstall
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 X
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.