Most intelligent persons of the world

[i3670]

learned one language per day.

Not possible. To completely learn a language takes a lifetime. We're talking hundreds of thousands of words. French has a relatively small number of words, about 100,000. Assuming he slept for 8 hours and didn't stop learning words while he was awake, that's 2 words per second, leaving no time to master the grammar or pronunciation.

Maybe he could learn to repeat a few sentences and so seem to be conversant on a given topic.

That all depends on what one means with learning a language. Do you know a language when you know all the words and how to use them? Or do you know a language when you know how to use it in its basic form? If one follows the first question, that means I do not know my mother tongue because I do not know all Swedish words.