First cut the fruit into small pieces or allow it to drain if you use canned fruit. I particularly recommend the combination of strawberries and bananas, or canned pineapples and tangerines. In principle, you can take anything you like, just not fresh pineapple.
Then stir the quark with the cream and vanilla sugar until creamy and season with sugar (when preparing canned fruit you can also add a little of the juice, then possibly add less cream). Finally fold in the fruits.