Translation of immature in German

I want to improve my level of English. Have you ever been in the U.S. and in which states have you been? I've been in England, Scotland and Ireland, but unfortunately, I have never been to America.
Anyway, I will add the 'offending' word feature within a few hours and write you an email once it is up and we will give it a try. Do you agree? Did you get my message? When do you want to start translating for me?
I'm from England and am learning German. Maybe we can share tips and tricks. How's your level? If you want to practice together, we can make voice over IP calls and write letters and correct each other.