I want to buy ExcelPort - Product / Category / Customers Excel Export / Import  Module . But I want some information from you. I added some fields in oc_products table in my database like book name , author name . So is it possible to export and import that details ?  and second thing You provide document file for how to import and export products ? Give me answer as soon as posssible.

ExcelPort comes with a documentation in the ZIP describing how to export / import.

It seems you have added custom fields in your database, which are unknown to ExcelPort and default OpenCart, and they will not be exported. In order to be exported, ExcelPort should be modified to add those fields in the export functionality. The modification can be done either by your developer or by our developers via our paid services.