How to restore hidden toolbar in Firefox
I’ve accidentally hidden the menubar navigation items and can’t see File – Edit – View anymore.
To turn them back on, try pressing your alt key. If that doesn’t open a menu, try holding alt and click somewhere on the screen. This should restore access to them again. If that didn’t work, you may have had another menu open at the time.
And this will work if you’ve also added plugins or extensions that are giving you grief.
Try closing Firefox and try restarting it in safe mode.
If you’re missing a link to start Firefox in safe mode through your start menu / desktop / gnome / kde / other, you can start it from the command line with a switch.
In the dialog that first pops up, check Reset toolbars and controls.