Stir fried fish with chinese celery (pla pad kuen-shai)

Ingredients

• 300 grams fish fillets, cut into well pieces
• 2 tablespoons minced garlic
• 100 grams scallion, cut into 1" long
• 150 grams chinese celery, cut into 1" long
• 2 red chili peppers, sliced diagonally
• ½ cup soup (or water)
• 2 tablespoons soy sauce
• 2 tablespoon soya bean sauce
• 1 tablespoon oyster sauce
• ½ teaspoon sugar
• ½ teaspoon ground pepper
• cooking oil