Safari will not close

Adware is installed on your Mac.

You can remove adware/malware using Malwarebytes for Mac.

    Use  the latest release of MalwareBytes for Mac to remove malware/adware. 

     Install guide:       https://support.malwarebytes.com/docs/DOC-1817

     Uninstall Guide:  https://support.malwarebytes.com/docs/DOC-1190

     The installer may ask you to allow it in Security & Privacy  /System Preference. Allow it.

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

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

The developer of Malwarebytes for Mac is an active member of this community.

I , like most of the members of this community have been using this for years.

Personally I wouldn't think high of any rating offered by anybody from internet.

I don't know any other better app.

+1 for Malwarebytes. Safe, effective, and doesn't damage your OS.