Hi everybody,
I’ve not noticed any topic like this one, so I’ve created it 
if somemone wants to share his/her relationship with languages during his/her dreams, this is the good place to do it!
In my case, there was a clear relationship between languages in real life and languages in dreamland. As long as I remember, I always dreamt in my mother tong - i.e french. But when I went in a english-speaking country for one year, I started to dream in english. Not each dream was in english, most of them were still in French. Some were only in english. But the majority of my english-speaking dreams were actually bilingual dreams: in english and french.
When I came back to France, I also came back to monolingual french dreams.
Then I started to learn spanish. And with spanish came spanish-speaking dreams. At the beginning they only consisted of dreams where I was in Spain and, unable to speak correctly the language, I was answering in French or English to DC - who spoke perfect spanish!
Finally, I lived in Spain for one year. And I started to have bilingual or even trilingual dream.
A few trends I observed about my bi/trilingual dreams:
- They mostly happen when I’m not in France but in another country (so I’m compelled to speak english or spanish everyday)
- When I start learning a language, I don’t speak it fluently in my dream, but some DCs do!
- Sometimes my dreams were only/mostly in english or spanish but there was a french voice-over
- Very often, language depends on DC. Some DC only speak one, some speak other, some speak several…
- Probably half of my bi/trilingual dreams are linked to trips or to university, but I can have travel dreams only in french (and I can have action dreams with spanish or english)
- Strangely enough, the DC of a real friend doesn’t always use the same language than the real friend does. Most of the time, the DC of my American friend talks to me in english, but once or twice, he texted me in french!
My record in a language dream is 4 different languages. It happens when I visited Porto. I dreamt I was visiting the city and I went to a tourist office. I started speaking with the receptionist in French but I thought her level was low, so we switched to english. That was perfect but she wanted to switch to Spanish. We did it, I anew thought her level was bad, so we switched again to english. Then, at the end of the talk, I thanked her in portuguese (“obrigado”, the only word I knew in this language ^^’). She answered me “you’re welcome” in portuguese. I didn’t know this word, so when I woke up I checked online if what I heard in my dream could have been the real “you’re welcome” in portuguese and found out it wasn’t at all ^^’ but at least “obrigado” was portuguese, and so I have had a four-languages dream (yeah, one of this language is only one word, but… 
)
If you have any experiences/obsvervations about languages and dreams, you’re welcome to share it here