It's unclear where in the interface you are seeing the problem, but it's probably in Kodi core or the Estuary skin.
If in Kodi core, the Dutch localisation was installed through an add-on, so the files are in /storage/.kodi/addons/ and you can edit them and restart Kodi (or reload the skin via kodi-send commands) to effect the change. Note that any bump to localisation addon upstream will result in the addon updating int he background and your changes will need to be reapplied.
If in the Estuary skin, the translations are contained in the skin addon which is embedded in the read-only part of the LE filesystem under /usr/share/kodi/ and you cannot edit this location. So you need to clone the skin to /storage/.kodi/addons, then change the skin name and change the translation, then select/enable the modified/renamed skin in Kodi settings. Note that any changes to the upstream skin will not be automatically applied. Probably not a big deal but skins do receive maintenance fixes over time.
If you want to fix the root cause for the future, you need to register with https://kodi.weblate.cloud/ and submit a change to the required set of translations; either Kodi core or the skin (wherever the translation resides) and then it'll end up in the LE image via maintenance updates that we make over time.
The alternative option is educating the user to understand that "Instellen" is how/where you setup? movie sets.
Fixed it manually, and reported.
