My favourite part is when he states: "I want to keep this country as we have inherited it from our forefathers. And it should remain this way..."
You'll notice that a Professor Patzelt was brought in to respond to Alexander Gauland. Patzelt did not follow the narrative either. He agreed with Alexander Gauland that the existing German population would effectively be replaced through a process of ongoing immigration, but unlike Gauland, he supports this on the ground that Germans are not having enough children (which they aren't).
The interviewer is clearly perturbed by the fact that her subjects are talking about the German people being changed or replaced by immigration, but she is showing a lack of logic and foresight in shying away from recognising this. As much as I disagree with Professor Patzelt's support of open borders, at least he is willing to acknowledge the logical consequences of the policy.