Hi,
You're probably installed an old version of HikaShop years ago and got the nl-NL fil at that point and didn't update it since then.
If you go in the Languages tab of the HikaShop configuration page and edit your translation file, you can see a button at the top "Load the latest version from our server". This buttons needs to be clicked on if you want to update the translation file.
Also, on that same page, if you scroll down in the text area on the left, you'll see at the bottom the translation key HIKA_LANG_VERSION with the version number of HikaShop for which your translation file is.
If you have the latest version of the translation file, you should have:
HIKA_LANG_VERSION="4.4.1"