Use Quen mostly, but when you can, hit the mage with Igni. Dodge his sand attacks and at all costs, stay away from his whirlwind. This was a pretty challenging fight the first couple of times. Then focus on the mage, who is quite powerful. Best way is to draw the swordsmen away from the mage and dispatch them first. Soon after you will be on a beach in a fight. When the guard come to you and you have the QTE to ask them to meet the captain, choose the last option for some extra XP. You’ll have a cellmate who’ll attempt to teach you the language. Somehow or other, you will find yourself on a ship on your way to Olfiri to answer for your actions.