Word removes screen elements like menu bar, toolbars, and scroll bars when you open a document in full screen mode. You can turn off full screen mode to restore your toolbars and menus.
When document is open, do one of the following:

• Press ALT+V to display the View menu, and then press U to turn off full screen mode.
• If the Full Screen toolbar is visible, click Close Full Screen.

To turn on default Toolbars press T when menu bar is open. You can use keyboard shortcut “Ctrl+F1” to toggle the Ribbon tabs on and off.