Concerning the "fourth line":
HOW can you "yanchang" prolong business hours, SINCE you are open seven days a week from 9 to 9?
Are you suggesting new buyers to open on "eighth" day of the week? Is this what you mean?
As far as Staffs concerned, that only two staffs needed is not correctly described (Quan Zhi he Jian Zhi Ge Yi Wei, as you stated).
How many persons work in the shop each day? Four? Am I right?