I have made some preparations for the trip to New York City!
I have bought tickets to go to Liberty Island, and a friend recommended me the best price for (18 bucks for it was good).
The most important preparation for the trip is the ESTA (Electronic System for Travel Authorisation), which I have to apply for to get into the US, even though I´m having a layover. The thing is valid for 2 years and are allowed to spent 3 months in the US during that time period!