How do I make a radio documentary?

"Staring red-eyed at the mirror in front of me, having spent another day and half of the night with my computer, I ask myself fundamental questions: Why radio? Why documentary? Answer: No other medium can provide me with more freedom of creation and investigation. It meets my urgent interest in reality and the desire for a 'musical' expression. The material (der Werkstoff) is sound. And sound always surrounds us. And: I'm not so much interested in the description of stable situations, but in processes. Our medium is not space, but time; our stories are not glued to the ground, but have motion, life ... That's why!" (Helmut Kopetzky, German author)