Is it normal that i drink 1,5l of water at one time ?

Probably not a good idea. There is such a thing as water poisoning. Yes, you can die of drinking water too much, too soon. Google it.

You probs don't need that much, there is water in fruit and vegetables and other things. You might damage your kidneys doing the 1.5l in one go.

I don't think that's normal.

1.5 liters of water? Isn't that like 6 cups in one shot? Wouldn't it be better to drink 8 ounces every hour or sixteen ounces every meal(if you eat breakfast, lunch, dinner, and snack)?

Why not take sips during the day? you're more likely to retain it, less trips to the loo and it will be put to good use by your body as opposed to loading up in one go and rushing to the loo every 15 minutes.