Both of these phrases were spoken by the character of Blanche DuBois in two separate poignant moments in the play.
When she says Voule-vouz... she is speaking to the young man who was delivering to the house. She had had a couple of her usual drinks already, and once she does that, she reverts back into time. When she goes back in time she often revives her traumas, and her mistakes. In this case, she was enthralled by the boy's youth. We also know that she had an affair with a 17 year old when she was a teacher. Hence, in the middle of her foggy brain she began to try to lure the boy and asked him the question of "would you like to sleep with me tonight?" in French but it was as part of her drunken stupor.
The phrase of "fire! fire!" was Blanche's reaction to Mitch's exposing her for what she really was. It was a metaphore. When he tore up the lamp saying that he wants to see her under real lights (as she was conceiling her age), the "light" that showed up enlightened him, whereas it diminished her. It was her last call for help, and she lost it. Hence, in desperation, she yelled "fire!" which was in fact a metaphore for her denial of "the light" showing her face.