Translation
Natasha speaks over a dozen languages fluently, without any trace of foreign accent if that's what her work requires. It's skills she picked up in Red Room and SHIELD, but mostly when she was on the run. Good ear for languages and some time in a country where a foreign one is spoken – and she's mastered it.
It doesn't mean she feels comfortable using any of them.
There are still so many things she doesn't understand but she never complains. She acts because that is what she is supposed to do; appears comfortable and at ease and familiar, leaving all the questions to herself. Only sometimes, she asks Clint or Phil, recently Bruce or Thor or Steve because they are all somehow maladjusted.
Natasha remembers very little from the times before the Red Room. The program was to make the Widows dehumanized; it never felt like home, neither did any place when she was running. America is still strange to her and it's not her homeland. That's what she's been turned into: a person without something to compare the world to, a person without a language to translate the world into.
All those years are just twisting in the wind.