I found the solution and I'm posting it in case someone else have the same problem.

The answer is to create relational tables as following, instead of having one table with all the data in it.

Table Sales (SalesID, SellerTypeID, ShopLocationID, ItemCategoryID,ItemConditionID, Sold, Price, ShippingCost)

Table SellerType (SellerTypeID,SellerTypeDescription)

Table ShopLocation (ShopLocationID,ShopLocationDescription)

Table ItemCondition (ItemConditionID, ItemConditionDescription)

Table ItemCategory (ItemCategoryID, ItemCategoryDescription)

Regards 🙂