Chop the onions and fry them with the bacon. Clean the potatoes, carrots and celery, cut into pieces of about the same size and add. Sweat briefly, then add 1.5 liters of water and add the lentils. Add some granulated broth, bring to the boil and cook until the lentils are soft. Then season the soup with salt, pepper and vinegar.
Add sausages to taste and let them get hot, then serve.