Well it's August now and some close partially for vacation, others reduce their hours, others in the main central area will continue as they have.
Sundays, however, isn't the best shopping day. Most boutiques and clothing stores are closed. You'll find some grocery stores open, as well as all restaurants/food places open, some stores that cater to visitors in the center but there is no set rule on hours or closures, so it depends on the store. Just keep in mind Sundays year round mean being closed as a general rule.