How to configure the file to update so that duplicate products are not created?

Go to the basic configuration of the file:

In the "What the file contains" section, select the option

File ID

Optionally you could link file with products using file ID.
Linking is useful, for example, when you import the same product from several suppliers.
File and product linking is done during the first import or in the "PShowImporter" tab in the product edit in Back Office.
When updating data, use the file ID, if there are products in your store assigned to this ID. Otherwise, no data in the store will be updated
Linking a file to a product is useful when you integrate a store with multiple feeds. With linking, one integration will not disable products added by another integration, when you use the option "disable products not available in the file".