How to pay taxes in Slovenia as an affiliate marketer?

Hi. My name is Kristjan, I am from Slovenija and I am an affiliate marketer. I am selling a high ticket digital course called Legendary Marketer. So my question is, how could I pay taxes, as a freelancer? I saw a video on Youtube, that talks about paying only 4% tax in Slovenia as an SP. And under the SP tax regime, you can opt for lump-sum cost, which I really don't understand and I would really appreciate, if someone could explain to me a little more about it.
Thanks :D