Hello guys⚘ I'm Parsa and I'm planning to study IT/Game in NL. I'm currently studying mathematics theories diploma (iranian high-school) and the last semester will be finished by July 2023. Can someone tell me what should I do in order?

Your diploma wouldn't matter much for applying. I assume that with that diploma, you'll still be able to join the study. The only thing you'll need is a certificate of your level of English. You should look into Cambridge or Anglia exams to get such a certificate. Hope this helps!