Ah... the 'dashboard' is the IKE or Instrument Cluster.

The Instrument Cluster can only present the text in one of 6 languages: GB, US, DE, FR, IT and ES

The closest you can get to what you want is Dutch on the Mk4 nav (menu + spoken) and English or German on the IKE.

The Mk3 nav never had NL as an official language, so if you have a Mk3 nav and wish to make it NL, you must translate all of the text yourself, using the Mk4 NL text as an example.