Stuffed pasta shells with cream of ricotta

500 grams pasta shells 250 grams peeled shrimp 250 grams of crab sticks Celery 1 large onion 2 tomatoes Mozzarella cheese Cream of Ricotta cheese 1 cup of Ricotta 1,1/2 cups of milk depends on the desired thickness Salt, pepper and paprika powder 1 tablespoon of butter 1 teaspoon of garlic paste