Hi Saguaros,
Thanks for your reply! I spend some time this weekend browsing the website of Snipcart and changed the code a bit so now it is using the 3.0 version of Snipcart. By doing this it changed the appearance of the cart but also it picked up the site language (in my case Dutch) so for me the problem is solved.
I think when you use the Samba Spa template the version of Snipcart is still the 2.0 version. I recommend everyone to update to the 3.0 version. By doing that you don't need to override any code for the language and another problem I had was that the 2.0 version did not look to be responsive on mobile phone displays which the 3.0 is. So that problem you will also solve by updating the code.
Anyway, many thanks you wanted to help me!