How can I have translations for my subdomain I setup Craft with one domain-1, now domain-1 has sites domain-1Global and domain-1NL. On this domain, the translations work perfectly. 

But now I added a second domain, domain-2 with the sites domain-2Global and domain-2NL. When I access the base url from the domain-2NL I get the template for the homepage of domain-1NL. 

I tried removing the define('CRAFT_SITE', 'domain-1'); in the web folder, this worked for a while but ultimately failed. Does anybody know a different solution?
I'd double-check your index.php files for all domains and make sure they're all using the correct handle in the define('CRAFT_SITE') code. Sometimes I copy/paste files between sites and forget to update the site-specific variables.

I'd also make sure the Base URL for each site is correct in the settings. 

Also make sure the section your homepage uses isn't set to the wrong propagation method.