Comment by xormapmap

The idea that child brains are better at learning languages is a myth. Adults struggle with languages because traditional language education is not fit for purpose. If you took a child and isolated them in such a way that they never got comprehensible input, and instead only gave them traditional language lessons (think textbooks, grammar drills) - they too would struggle. The good news is that if you take an adult and give them comprehensible input like you would a child, they will learn at least as effectively as a child.