Earlier in this course we learned about ways of indicating possession. In that lesson we learned that one way of saying that you have something is using "Mae ... gyda fi/chi/e/etc." For example, "Mae car gyda fi" means "I have a car".
If you use that same structure, "Mae bargen gyda fi" would mean "I have a bargain", and "Mae bargen gyda chi" would mean "You have a bargain". To make it a question, you change "Mae" to "Oes". So "Oes bargen gyda chi?" means "Do you have a bargain?"
Right, I understand the grammar, just not what the situation would be. I think I have only referred to bargains as something that was OFFERED by a seller, GOTTEN by a buyer, or MADE between two parties. I just don't understand who would "have" it. I thought "to have a bargain" might mean something specific in UK English.