how do I reinstall Safari

Update or reinstall Safari for your computer

Reinstalling Safari

If you deleted Safari and don't have a Time Machine backup or other backup, reinstall macOS to put Safari back in your Applications folder. Reinstalling macOS doesn't remove data from your computer. 

Before reinstalling, you might want to use Spotlight to search for Safari on your Mac. If you find it, but it's no longer in your Dock, just drag it to the Dock to add it back.

https://support.apple.com/en-us/HT204416