Heat the oil in a large, heavy-bottomed pot over medium heat. Add the onion, celery, and carrots. Cook the vegetables, stirring occasionally, for 4-5 minutes, or until the carrots are just becoming tender and the onion is starting to become translucent. Add the cabbage. Continue cooking, stirring often, for 8-10 minutes, or until the cabbage is very tender and browning lightly at the edges. Stir in the tomato paste, both types of paprika, and salt.
When the tomato paste is evenly incorporated into the vegetables, add the tomatoes, broth, bulgur, and navy beans to the pot. Bring the mixture to a boil, then turn the heat to low. Cover and simmer for 25 minutes, or until the bulgur is tender, yet still chewy. If the stew is a bit too thick for your liking, stir in an additional 1-2 cups / 240-480ml additional broth. Taste the soup; adjust the salt as needed and add white wine vinegar, one teaspoon at a time, to taste. Divide the soup into bowls and garnish according to your preferences.
The soup can be stored in an airtight container in the fridge for up to six days and frozen for up to eight weeks.