Rinse the lenses briefly under cold water. (You don't have to soak them.) Clean, wash and cut the soup greens into small cubes. Peel and chop the onion. Wash the lovage.
Heat the oil in a large pot. Sauté the vegetables and onion. Add lentils, lovage, bacon and 2 l water and bring to the boil. Simmer covered for 45-55 minutes.
Peel, wash and cut the potatoes into small pieces. Add to the lentils about 20 minutes before the end of the cooking time and cook everything ready.
Cut the sausages into slices. Lift out the bacon and cut off the rind. Cut the bacon into small cubes, removing any cartilage. Take out lovage.
Add the sausages and diced bacon to the soup, heat briefly. Season with about 2 tsp salt and 1/2 tsp pepper. For the sweet and sour version, season additionally with vinegar and 1-2 teaspoons of sugar.
For the Italian version: Cut salsiccia sausages into slices and fry them in hot oil. Instead of the wieners, add them to the soup. Season to taste with balsamic vinegar and 1-2 teaspoons of sugar.