Press F10 or press and hold the Alt key down to bring up the "Menu Bar" temporarily.

Go to "View > Toolbars" or right-click the "Menu Bar" or press Alt+V T to select which toolbars to show or hide (click on an entry to toggle the state).

See also What happened to the File, Edit, and View menus? and http://kb.mozillazine.org/Toolbar_customization

   Make sure that you have the "Bookmarks Toolbar" visible: "View > Toolbars"
   Check in "View > Toolbars > Customize" that the "Bookmarks Toolbar items" is on the Bookmarks Toolbar
   If the "Bookmarks Toolbar items" is not on the Bookmarks Toolbar then drag it back from the Customize window on the Bookmarks Toolbar
   If you do not see the "Bookmarks Toolbar items" then click the "Restore Default Set" button

You can check for problems caused by a corrupted localstore.rdf file.

• http://kb.mozillazine.org/Corrupt_localstore.rdf

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe Mode start window.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes