In both cases you will receive sound and visual notification of the status of your order. Restaurants have the option of sending you an alternative offer that is different from your original one, to which you choose to answer. If you want to receive a notification, notifications must be turned on in the settings on your phone and the sound must be switched on.
On the meal screen , below the name of the meal you have the option to choose the quantity and then you click on the green button ADD TO ORDER. A shopping cart icon should now appear in the upper right corner of the meal screen and when you click on it you can enter the cart screen. Now you can checkout or you can continue shopping.