How can I delete this: “Thema doorColorlib Aangedreven door WordPress”?
Are you asking about the footer credit?
you have to buy a license first, do you have a license of the template?
No, I have no license because I want try this template first. Where can I buy this license?
IN order to remove footer credit you have to obtain a license, Licence - Colorlib
But just for checking template, you can leave it as is, once you decide to use this template you can buy a license and then we can remove credits