Refund and Return Policy

I have a new marketplace that will lunch soon. The marketplace will be integrated at the beginning with Shopify where it will be listed as one of Shopify sales channels. I need consultant to create a fair return and refund policy for Merchants. On the other hand, it is still convenient to the customers.

The following products types are prohibited on the marketplace so need to consider them:

Drugs.
Medical drugs and medicines.
Alcohol drinks.
Food.
Weapons
pornography content.