How to hide the bar above the tabs in the Mozilla Firefox browser

Question

As you can see, there's a bar above the tabs in the Mozilla Browser which gives redundant information. It happened when I updated some extensions but I don't know how to remove it.

Answer 1

It is the title bar of the firefox application. To disable, click the hamburger menu (☰ button on the right), select "Customize..." and on the left bottom, remove the check from "Title bar".