Season pork chops with salt and pepper. Dredge chops in flour, shaking off any excess. Reserve 2 tbsps of flour. Heat oil in a large skillet over medium-high heat. Fry pork chops 3 minutes on each side. Remove chops from skillet and set aside. Sauté onions, celery, bell pepper and garlic for 5 minutes. Add reserved flour and stir into vegetable mixture. Pour in beer and beef stock. Return chops to the skillet, reduce heat to medium, cover and simmer for 1 hour or until chops are tender. Season with salt and pepper to taste. Serve with your favorite German side dishes such as potato salad, boiled potatoes, cabbage or Brussels sprouts.