What is the language of communication between you and him?

English as a Second Language English Vocabulary, Grammar and Idioms
1
  1. It is very difficult for me to change the language of communication with a person that I’ve known. I’ll stuck with the same language that I used the first time.
  2. It is very difficult for me to change the language that I used to communicate with a person the first time. I’ll keep using the same language to communicate with the person.
  3. What is the language of communication between you and him?
  4. What language do you both communicate in?

Are the above sentences correct? Please advise.

2
  1. ‘stick’ - but the statement is over-complicated. There’s no point in saying ‘language of communication’.
  2. is over-complicated.
  3. OK but strangely worded.
  4. OK

I suggest:
1 and 2) It is very difficult for me to change the language I use with a person. I tend to stick to the language we originally conversed in.
3) Which/What language do you use to speak to/converse with/communicate with each other?