@lproven Some research on how and when babies learn to speak has shown interesting results. All languages bar one has the same range of results.
Danish is sufficiently hard to learn that even children of native speakers take longer to learn it properly than for any other language. The most likely cause is the bewildering array of almost identical vowel sounds.
Early vocabulary development in Danish and other languages: A CDI-based comparison | Journal of Child Language | Cambridge Core
Early vocabulary development in Danish and other languages: A CDI-based comparison - Volume 35 Issue 3
Cambridge Core (www.cambridge.org)