Children can learn 2,3,4 languages when young, but easier if they are 6 or younger...
Consider Swiss children ...In their country they speak French, German Italian ...The children learn those languages plus English...
There’s also a couple areas in Switzerland where they still speak Romansh (Latin).
Some Swiss also speak Romansh.
I learned to speak German at age 35. Total immersion is the only way. Went to Germany and didn’t speak English for 5 months. Keep up with it by reading; especially dialogue so plays are a favorite.
Oriental business friends never get our colloquialism at all. You have to be careful and avoid our normal speaking patterns.
Even Germans don’t always follow our casual conversations, and they’re very cood.
True, my first language was Parisian French, and English then Italian.
Latin was easy. and I can usully decipher Spanish.