French phrase
Depuis combien de temps pratiquez-vous ~ ?
Meaning
How long have you been practicing ___?
When to use it
Asks how long an activity has been ongoing. It is polite and suits hobbies, lessons, and sports.
Example dialogue
Depuis combien de temps pratiquez-vous le piano ?
How long have you been practicing the piano?
Depuis cinq ans.
For five years.