If you’ve already read through this and understand what it means and are still worried about your privacy, I would recommend you switch to LibreWolf - it takes all the best practices of hardening Firefox for security and works out of the box. Unfortunately, this means you can’t play certain videos, it doesn’t auto-update, and some - likely many - websites will break/not work. This is the price to pay for true privacy. If you don’t want that, just keep using Firefox.