Exiting the PDA
At the end of your shift, or whenever you put the device away, exit the PDA so that nobody else can take orders under your name.
On the Orders screen, tap the arrow at the top left to go back to the employee login screen, and there tap Exit PizzaGest.

The PDA confirms that it has been closed. The Log in again button takes you back to the start screen.
If only the waiter is changing, there is no need to exit: go back to the login screen and enter the other employee's code.