If you are in a shop when salah is called, you should leave.
Restaurants generally close during prayer times.
If you are in a restaurant when a prayer call occurs, you may be allowed to remain in the restaurant. Some supermarkets eg. Al Azizia and Tamimi, will allow you to continue shopping during prayer times but the doors are locked and you will not be able to go through the check-out stands or leave the premises until after prayer time is complete. The same supermarkets are also open all night. The Islamic calendar is based on the beginning of the Islamic era, and dates from the year of the Hijrah, the emigration of the Prophet Muhammad from Makkah to Madinah.