Change the theme to anything other than the System theme.

Do you get the buttons if you enable the title bar or the menu bar via buttons at the bottom of the customize page ?

• https://support.mozilla.org/en-US/kb/customize-firefox-controls-buttons-and-toolbars

it solves partially my problem but looks ugly now

thats how it looks like in chromium (way better)

Did you try changing to the Dark theme?

Firefox would normally display the window control buttons on the Tab bar if both title bar and menu bar are hidden.

You can check with the Browser Toolbox if those buttons are present in the DOM and possibly hidden via CSS what could be overruled via userChrome.css.

• https://firefox-source-docs.mozilla.org/devtools-user/browser_toolbox/

solved reinstalling it from apt from this guide (https://www.omgubuntu.co.uk/2022/04/how-to-install-firefox-deb-apt-ubuntu-22-04)