Negociate a product
In order to negotiate prices you can send a message to the seller on the product page by clicking on "Contact the seller" below "Add to cart". You can then discuss with him in order to agree on a price.
You can also make an offer (directly or after negotiation) by clicking on "Make an offer" below "Add to cart". Then, you propose a price for the desired product (excluding delivery). As for the Selency delivery prices, they are fixed, you cannot negotiate them.
Good to know: you can make an offer on a product only if the seller has authorized this option (except when, through messages, he accepts a negotiation, you can ask him to make this option available on its product ad).