0Learning how to spek a new language, especially when you know multiple languages can be challenging.
The easiest trick is to think in that language. Translating in your mind spoils the vocabulary and the grammar. This of course requires practice, and unlearning what you already know! Each language is unique, and has its nuances.
Also, it depends a lot on the culture of the place as well. Lots of idoms and pharses are evolved from a culture. Knowing a place, its history, culture, way of living also gives you a lot of insight in learning a language. It also makes it very interesting.
All of the above points will help you learn a new language, no matter what your age. But most of all, remember to enjoy yourself, and its easy! :)
