There is a physiological equation to consider in learning a new language. That is age of the individual. When you are young, before your late teens, learning a new language can be done in only a few weeks. A child's brain is like a sponge. Absorbing anything and everything. As you get older it becomes more difficult. I have been told that trying to learn a new language in your 60s or 70s is nearly impossible and at best extremely difficult. My understanding is that the portion of your brain, that allows for learning something like a language, diminishes so greatly by the time you are a senior citizen. Don't know all of the medical reasons for this.