Website design is a strategic execution of combining several things together. There are several aspects that a designer takes care of when it comes to executing a design process. While one business may demand a simple and static design and has minimal information to display through visual aesthetics, the other one might want a more responsive design while having a large set of products to display for the customers. Both are different sets of requirements, and not all businesses are the same. Therefore, only a professional designer who analyses your business requirements can tell you how long it will take to design your website.