If you are interested in starting an epistolary relationship with some one but haven't a clue how to write in the person's language, you may benefit from the services of a correspondence translation professional.
Even in the event that you do understand your intended pen pal's language, it may prove difficult for you to understand the nuances of colloquial writing and it's definitely possible that you may be in store for some embarrassing gaffes whilst writing letters to your intended recipient.
So if you want your letters not to be misinterpreted, it's best you seek the help of a professional.