Tap on "Play now", select a language, choose the option "Friends" and tap on "Play now" again. There, you'll be able to enter the name or nickname of the user you wish to play with. Finally, tap on the player's profile for the game to start.
Go to Menu>Friends and search for said user. Once you find them, you'll see a "Reproduce" button which, when tapped on, will let you chose the language you wish to play in. Tap on "Play now" for the game to start.