Hey Jelle, welcome to the forum!
Since you are young and in the Netherlands, have you checked out the NFN-Jongeren youth group yet? It's home to a small couple hundred teens just like you! Some with lots of experience and some just starting out, but all loving to be nude and we organize youth camps and other fun activities too.
Getting to know more naturists your age might make it easier to get started visiting beaches and other naturist venues too

it certainly helped me.