The problem is that your friend has created the account in the Dutch version and therefore he can not find you because you have created your account in the world version.
OSM has two versions: WORLD and DUTCH.
"Peace cannot be kept by force; it can only be achieved by understanding" - Albert Einstein | "There are only two ways to live your life. One is as though nothing is a miracle. The other is as though everything is a miracle” - Albert Einstein | "Learning by making mistakes and not duplicating them is what life is about." - Lindsay Fox | "Everyone makes mistakes in life, but that doesn’t mean they have to pay for them for the rest of their life."