How does it only take a year or so to speak/understand our first language but it’s so much harder to acquire another language?

Question

Like, we have a frame of reference (first language), so why is it so hard to learn another language after that?

In: Other

Answer 1

Any language I’ve learned for a year, I will put my fluency against any one-year-old native speaker.

They might understand considerably more words than me, but I can tell jokes, form thoughts, make small-talk and say what noises animals make better than any fucking baby you throw at me.

The brain starts growing mylin, the native speaker kid is going to win every time over all but the most dedicated adult polyglots, but your title is phrased in a way that made me imagine doing a rap battle against a French baby.