How long doest it take to learn a language?

Kia ora!!! I'm gonna ask you a question...how long do you think it takes to learn a foreign language? well my English is quite basic, but I make great efforts to improve it!!! I'm coming to the amazing New Zealand in june and I'm going to stay there two months, i will be hosted in a host family and i'll attend a school...do you think it is worth it?, or rather do you think i will be able to understand songs and movies after my stay? i'm looking forward to receiving your answers, the last thing, i'd like you to correct all the mistakes i've probably done...THANKS!!!!