Heat the olive oil in a large frying pan or wok over medium-high heat. Add bell pepper, carrot, and celery and cook for 3 minutes, stirring frequently. Stir in shrimp and cook, stirring frequently, for 2 minutes more. Stir in the pineapple chunks. Cook for 1 minute. Lower the heat and stir in the prepared sauce. Cook for 1-2 minutes, stirring constantly, until shrimp are pink. Pour in the cornstarch and water mixture and continue to stir until the sauce thickens and has coated the shrimp and vegetables, about 1 minute. Remove from the heat.