When is a contract concluded between two parties for the supply of goods considered, in principle, a contract of sale and purchase, and not a brokerage contract?

A contract concluded between two parties for the supply of goods is considered, in principle, a contract of sale and purchase, unless the claimant provides conclusive evidence proving that the relationship was one of brokerage, especially if the contracting party negotiated in their personal capacity and achieved a significant profit margin, and their statements regarding the nature of the relationship or the delivery of the goods were contradictory.