Heat oil in a light-bottomed large wok.
Once the oil is hot and shimmery, add garlic and ginger and saute for 3-4 seconds.
Now add onions and saute for 10-15 seconds.
Add bell pepper and mushrooms and fry until the mushrooms are browned and their moisture is evaporated (1-2 minutes), stirring frequently.
Add rice, soy sauce, vinegar, black pepper, and salt. Be very careful while adding additional salt as soy sauce is also very salty.
Mix everything well using a spatula until the rice grains are coated with the sauce.
Add green onions and celery and mix well. Check for salt and sauces and add more as per your taste. Serve hot.