Boil the potatoes, peel, cut into slices and let cool. In the meantime, mix together the meat salad, mayonnaise, yoghurt, mustard, cucumber water, salt and sugar for the marinade.
Cut the herring into small pieces, the radishes into thin slices, and the pickled cucumbers into thin strips. Halve the eggs and cut into slices, the chives into small rolls. Peel and roughly grate the apple.
Add all ingredients to the marinade, then gradually add the cooled potatoes. The salad should be relatively compact.
It is best to prepare the salad the day before and stir it every now and then. Take out of the refrigerator about 1 hour before serving, it should not be too cold.