Every restaurant and indeed every household in Germany will have a different recipe for potato salad. I'm not in Germany (at least not usually) but I do make it occasionally. It's open to endless variation, of course.
This is an easy dish to make in advance for a party or a picknick, or just a hot day when you'd rather sit in the garden in the afternoon than cook.
Combine cream, mayonnaise, oil, vinegar, pepper, salt and paprika into a dressing.
Peel the potatoes and cook until they're just tender. Drain and let cool until you can just handle them. Cut into about 1 cm cubes. Pour the dressing over while the potatoes are still warm and put them in a cool place (not the fridge while they feel warm).
Chop the gherkins into pieces about the size of peas. Cut the pickled onions into halves or quarters. Cut green beans into pieces as long as they're wide.
When the potatoes are completely cool, mix in the other ingredients carefully. Refrigerate until use. It's nice to serve the salad on a bed of lettuce leaves, decorated with cherry tomatoes and other raw vegetables.