Wash potatoes thoroughly and cook in boiling water for about 20 minutes. In the meantime drain the beans in a sieve. Wash oregano, dab dry and pluck leaves from the stalks.
Peel and finely dice the garlic and onion. Clean, wash and chop the zucchini. Celery clean, wash and cut into thin rings. Drain potatoes, quench, peel and slice.
Heat the oil in a wide saucepan, fry the zucchini for about 3 minutes while turning, add the garlic, onion and celery. Season with salt and pepper and fry for another 3 minutes, turning. Add potatoes, beans, broth and half of the oregano and simmer for about 4 minutes.
Mix starch with water and thicken goulash with it. Season again with salt and pepper. Arrange in a bowl. Sprinkle with remaining oregano. Add sour cream.