It's easy to make Kartoffeln Salad (Potato Salad) yourself Skilli but I remember it as potatoes in mayonnaise, not in a vinegarette:-
Boil potatoes until cooked (but not mushy) and peel them if you want (I like the peel, so I leave it on). Chop them up to say half inch cubes, add finely chopped onion and real mayonnaise (I use the light or low cal version here but the original would be something like Hellman's)
whilst the potatoes are still hot. Add salt if you like it. Allow to cool and then chill in the fridge - you may need to add more mayo because the hot potatoes will soak it up! I then add chopped parsley or chives (whatever I've got handy).
NB "Lidl" is a supermarket chain that sells mostly German products at discounts -
http://www.lidl.co.uk/uk/home.nsf/pages/i.home