How to awake emacs gui after pressing ctrl+z

If you press C-z by mistake then you can add this to your .emacs to make C-z do nothing:

(global-unset-key (kbd "C-z"))

I did that after pressing C-z many times by accident.

Type

fg 

or

fg %emacs

to get Emacs back.

You may have to send the process a SIGCONT signal. You normally do this in the console by running kill -CONT $emacs_pid or killall -CONT emacs. If you insist on a GUI solution, you can try the task manager shipped with your distro.