colorful berries cake with refreshing lemon mousse

100 g butter 200 g graham biscuits 4 sheets gelatine, roughly cut up 500 g low-fat cream cheese 200 g whole milk yogurt 150 g + 2 tablespoons sugar 1 vanilla pod 100 ml lemon juice 200 ml cream 500 g of raspberries, blackberries, blueberries and redcurrants 2 teaspoons cornstarch 250 ml red nectar (cherry,…