Just updated. DON'T LIKE NEW LOOK. How do you rollback to old look without losing new security update?

Firefox encouraged to update for security reasons. Did so and ended up with a new look and new setup for the browser. Don't like it at all. Things in different places. Lost the navigation bar on update and had to go find it. Not happy with new setup at all. How do I get the old setup back? If removing the update is the only option that will happen. I have security. Bill