I “know” OOP

It comes for an interview. I ask general questions. We are talking about his current work and responsibilities. And I hear:
- When I arrived, there was generally horror. Well, I began to introduce OOP little by little, to rewrite everything to classes ...
- But why? What is the advantage of OOP over a procedural approach?
- In OOP, I can group functions into one class ...
- Why? Write them in one file. What classes are better?
- ... (the interlocutor’s stupor)

These were thoughts aloud