You could technically get poisoned from too much Vitamin C from the oranges but it would be impossible to eat enough oranges for it to become a problem.
But if you do eat too many oranges at a time you could have digestion problems that could lead to abdominal cramps and could also lead to diarrhea.
But other than that you're not gonna be harmed eating as many oranges as you can consume and it's impossible for you to consume enough oranges to kill you.
Eating oranges provides you with needed Vitamin C to help boost your immune system to fight off cold and flu viruses and even reduce your risk of developing other diseases.