On the Exchange Market you can exchange cards for Mondoz, for GOL, for success points or for other cards.
Only the exchangeable cards can be used on the Exchange Market.
The exchangeable cards are those bought with Mondoz in the Premium boutique (My Cards/More Cards? menu).
All the other cards purchased on the Cards Market and in the Success Shop are not exchangeable.
The starting cards (first team of bonus players of the tutorial) are not exchangeable.
Remember: if you exchange a card for GOL or for success points on the Exchange Market, the card becomes non-exchangeable.
There is a special card called: 'Unblocking Card'.
With this card you can transform a non-exchangeable card into an exchangeable one.
This card can be purchased with Mondoz on the page of the menu: My Cards > More Cards?
To transform a non-exchangeable card into an exchangeable one, go to your file (menu: My Cards > All my Cards), find the respective card and click on the icon that has the form of a green key, under the card.