If you can get a list of the number of times you communicated, like an email inbox, with the dates and times, you can use that.
If you are sending the actual conversations, then anything in Hindi should be translated into English or French. Send the originals too.
For official documents, you should use a certified translator. Technically, you should use a certified translator for everything, but then it becomes too expensive, so many people get their less important relationship evidence (such as emails, Facebook, whatsapp, etc.) translated informally - by a friend, or even themselves. If a friend does it, they can still send in the official translator's statement. If you do it, just be aware CIC does not want family members or the applicant or sponsor to be translating anything. The visa officer may accept it, but if it goes to an appeal it will not be accepted. Of course, we hope it won't go to an appeal.
