On the video I spoke the following sentences in the 5 languages -- Assamese, Bengali, Hindi, Spanish, and, of course, English: “My name is Naba Barkakati. I can speak in five languages.”
Just to give you a timeline of when I learned these languages... Assamese is my mother tongue, but I never learned it formally. I began speaking Bengali at 9 and all the way through age 22, but I didn’t learn it formally either. I studied Hindi in a language course in high school for 7 years. I learned English since I was 6 or 7, it was the language of instruction in school, spoke and used English in engineering school, and began speaking exclusively in English after I came to the United States, for more than 33 years now.
I started learning Spanish at age 53 and now when I speak in Spanish I am often trying to translate from English, which results in awkward sentences (hopefully, I'll learn to avoid translating with more practice). The strange thing is that for all my other languages, I am not translating thoughts from one language to another - - I just speak what I want to say and also when I hear, I just comprehend.
So, the question is how does the brain work for those languages that I learned when I was younger? Also, do we really think “in a language?' Or, are thoughts something more fundamental and not in any language. I feel like I think in English, but when I switch to languages that I learned in my childhood, I don’t seem to be translating from English. For those languages, it is as if I am able to simply switch my brain from one language to another. Anyway, I don’t have any answers to these questions, but perhaps these would be interesting research topics for someone who studies how people learn and retain languages.
Here's some more information to help you...
Although I don't really know the answers to the questions I posed, I did describe in an earlier video how I am learning Spanish, which you may find helpful for learning a new language:
Also found the following books that document the experiences of several language learners and sound intriguing enough to check out (I am reading Kató Lomb's book now):