Heat oil in a large pot or Dutch oven. Add onion and cook for 1 minute. Add garlic and carrots. Cook for 2-3 minutes, stirring frequently, to prevent burning.
Add in the tomato paste, tomato sauce and lentils. Cook for 1 minute. Add potatoes. Pour 4 cups of water on top. Add salt, pepper, thyme and oregano. Cover and bring to a boil. Reduce heat to medium-low and simmer for 25-35 minutes, until the lentils are cooked and potatoes are tender.
Taste the soup and add more salt and pepper if needed. Serve warm.