I don't know what … is about
I don't know what he's talking about.
I'm afraid I don't know what you're talking about.
Я не знаю, о чём Том говорил.
I don't know what Tom was talking about.
Дорогая, клянусь, я не знаю, о чём она говорит.
Darling, I swear, I don't know what she's talking about.
— Во время грозы (2018)
I don't know what you're talking about!
I don't know what this is about.
I have no idea what you’re talking about!