Is it permissible to work with a website that allows marketing its products for a percentage of the price, with the possibility of increasing the price, and undertaking delivery to the customer, and the customer's right to exchange or return, while not informing customers of the warranty period to avoid its legal details?

You are permitted to sell the website's products as long as it authorizes you to do so, for you are its agent, and the agent's hand is as the principal's hand. The agent must execute the agency within the authorized limits, provide the principal with necessary information, render an account, and return whatever belongs to the principal that is in his possession. There is no harm in relying on the seller's description of the product, provided that it is truthful and does not deceive the buyer or excessively exaggerate praise.