If you want to watch a video that tells his story, you’ll find a few available. I don’t recommend Bonhoeffer: Agent of Grace at all. Your time would be better spent watching Dietrich Bonhoeffer: Memories and Perspectives, which is a tremendous work. A secondary recommendation would be Bonhoeffer: Pastor, Pacifist, Nazi Resister. Although a good work overall, I disagree with the latter film’s premise that Bonhoeffer was a pacifist. They work unconvincingly to make him seem so, probably due to some agenda. Bonhoeffer was not a pacifist. He did, however, have an aversion to unjust war and a sensitive heart to the death of his fellow human beings.
If you want more info, I’ve written reviews on each of these videos along with reviews on several of the books I’ve mentioned. If you have to pick one book, read The Cost of Discipleship. If you have to pick one movie, watch Memories and Perspectives.