There is no one universally accepted theory of how a child learns a second language. For me is the best way not literally learning the language but having fun learning it. Language is learned not for its own sake but in order to communicate and to find out about the world. That is why I combine in language learning written and spoken language that is made comprehensible to children of all ages and also adults on different English levels, and engaged in different kinds of productive activities.

If you want to be able to speak without an accent, then the younger the better. Studies by Harvard University confirm that the creativity, critical thinking skills, and flexibility of the mind are significantly enhanced if children learn a second language at a younger age. Preschool years, especially the first three years of life, are believed to be a vital period in a child’s life. This is when the foundations for attitudes, thinking, and learning, among others, are laid down.

How long is a piece of string? It depends on what you mean by "learning a language". Even on the assumption that this means acquiring the language skills and vocabulary of an average native-speaking adult, there is still no simple answer to the question, since it depends on where and how the second language is learned, and the age at which it was started. Language learning depends mostly on three factors: the attitude of the learner, the time available, and the learner’s attentiveness to the language. If we assume a positive attitude and reasonable and growing attentiveness to the language on the part of the learner, how much time should it take to learn a language?

FSI research indicates that it takes 480 hours to reach basic fluency in English, and 720 hours in for example Greek.

If we are able to put in 10 hours a day to learn a language, then basic fluency in the easy languages should take 48 days, and for difficult languages 72 days. Accounting for days off, this equates to two months or three months’ time. If you only put in five hours a day, it will take twice as long.
Find out more: https://www.mother.ly/parenting/the-best-age-for-kids-to-learn-a-second-language