How do I remove this Malware from my safari?

Force Quit Safari. How to force an app to quit on your Mac - Apple Support

Relaunch Safari holding the shift key down.

Try YouTube.

For  more info:

Section: If you see pop-up alerts or ads

  https://support.apple.com/en-us/HT204759

Safari 12

Customize the website preferences.

When Youtube is running, open the websites preference and block the pop-up.

Customize settings for each website in Safari on Mac - Apple Support

 1. Use  the latest release of Malwarebytes for Mac to remove malware/adware installed on your Mac.

     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.

     Repeat the scan couple of times.

     Once done quit Malwarebytes for Mac.

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

2. Additional steps, if necessary.

 1. Remove unknown Login item.

     System Preferences > Users & Groups > Login items

     Authenticate and unlock the lock.

     Highlight the unknown login item (Mac Mechanic?) and click the “-“ button at the bottom left to remove it.   

 2. Remove unknown and third party installed extensions if installed. 

     https://support.apple.com/guide/safari/use-safari-extensions-sfri32508/mac

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

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

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