Sales work is mainly about the sales ability and related quality of sales staff. You can tell him that you like sales work, luxury goods industry and their company. That way, they won't ask you this question. Of course, you should know more about luxury goods and sales knowledge, show that you dare to communicate, be good at communication, grasp the selling point of a product well and actively safeguard the interests of the company.
This kind of interview is very easy. You just regard the examiner as your sales target and sell you to him. Don't be afraid of him, and don't make mistakes, which is necessary for salespeople.