Open Safari
Click Safari in the menu bar
Select Settings or Preferences
Go to the Privacy tab
Click Manage Website Data
Click Remove All
Confirm by clicking Remove Now
Go to the History menu
Select Clear History
Choose all history
Click Clear History
Go to the Extensions tab
Disable or uninstall unwanted extensions
Go to the Advanced tab
Enable Show Develop menu in menu bar
Click Develop in the menu bar
Select Empty Caches
Quit Safari
Reopen Safari