As shown in screen, there's issue with translated URL's, please check into this issue, either it should be only be,nl or fr-BE,nl-NL,but it's showing both
It looks like you have configured your WPML -> Languages -> Language URL format to "Different languages in directories". That means that the language directory in the URL will be the code of each language.
You can see what the code of each language is by going to WPML -> Languages -> Edit Languages.
If I misunderstood your issue, please try to explain it in a little more detail.
It would help if you could send screenshots of the issue and links to where I can see it.
The fact that the sitemap has links to all three languages, that is how it is supposed to work
If I understood correctly, the issue is that there are duplicate page links (three times the English link, three times Dutch and three times Belgian).