It’s tough to tell how much time he has had to learn as while he is technically only 11, he has lived in the US in the strip for around 20 years, although I see your point.
That’s straight cap. A photographic memory can help you memorize every single grammatical rule in every language if you would so choose. He might still have an accent but he should be able to speak decent English.
I’m curious to see how SPG would react to Femme Fatality