German phrase
In welcher ~ möchten Sie kommunizieren?
Meaning
Which ___ would you like to communicate in?
When to use it
It asks which language to use. It is a polite way to check someone's preferred language.
Example dialogue
In welcher Sprache möchten Sie kommunizieren?
Which language would you like to communicate in?
Am liebsten auf Englisch.
Preferably in English.