I speak plenty of languages with varying degrees of fluency. I'm sometimes asked what language I think in. A ridiculous question. For the first few years of my life, I only spoke Bengali. But I don't think in Bengali. I don't think in English either. And, whoever you are, neither do you!
The whole concept of "thinking in English" is nonsense. No-one does it. You think because you are human, and the language is universal. If you want to go somewhere, you don't translate the feeling of wanting to move into English before moving. When you are choosing things, you have the concept of what you want and then you search your mind for it. Sometimes you can't remember the precise word and stumble for a longer phrase or foreign expression to express the thought. But obviously the thought came first.
You see kids in Southall speaking a mixture of Punjabi, Hindi and English. They aren't thinking in any one of those three. As their mouths catch up with their thoughts, the first word that drops in is usually from one of those three languages. Some struggle with all of them.
It is so obvious. Yet people still use the phrase "I can think in x languages" as though it made sense.