Ted here from Shopify, thanks for reaching out to us!
I've taken a look at Blockshop's set up and I can confirm that there is an option to swap the theme's language to Dutch. On saying that, there are 292 translations missing as shown in this screenshot for example. You can always contact the theme developers support as well with any query before you purchase.
I'd recommend testing a theme first before purchasing as themes are considered a final sale and can not be refunded. If you are considering purchasing a theme, I'd suggest selecting the Try Theme button as shown in this screenshot. A trial of the theme will then be downloaded to the Online Store > Themes section of your admin. You will also be able to view or edit your language options as shown in this guide.
If there is anything else I can help you with, please let me know, I'm happy to help!
Thanks a mill,