Hello, due to International Copyright laws sometimes it is difficult to get music in one country that easy to get even in a neighboring country. I guess this is the case in between the Netherlands version of Spotify and the German version of Spotify in regards to this song.
Something else that complicates matters is that sometimes artists or record labels/aggregates allow their music to be allowed on a certain country's Spotify, but not another country (Spotify appears to be very earnest in making their entire catalog available on Spotify, but will only do so if they can do it legally). You can try contacting the artist (Oliver Helden) and he might be able to make his music avilable there (If he thinks this will be a good oppurtunity for him).
~Soli Deo Gloria~ * If you see a single asterisk like before this sentence, it most likely denotes sarcasm.