Safari will not quit

If Safari is hung, then try CTRL- or RIGHT-clicking on the Dock icon and select Force Quit if present. If not present then press COMMAND-OPTION-ESC to pop open the Task Manager. Select the entry for Safari then click on the Force Quit button.

  There is 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          Uninstall Malwarebytes for Mac

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

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