By changing the theme or the desktop environment. There a lot of experts here who can help you with that.
The presence of the tab bar and the menubar are coded into the widgets of the window.
So I can't remove it? But can I atleast lessen its size?
Yes, but not by much. The Menu item buttons will still keep it large enough to accommodate the buttons. It becomes rather pointless to remove 2 millimeters from the height of the bar.
The Menubar with the Menuitems is your toolbox.
That's where the users tools are, where they are organized and where they are found.
I see. Thanks