Who's your oldest friend? How long have you known him or her?
Who's your oldest friend? How long / you / know him or her?
Are you learning anything new at the moment (not English)? How long / you / learn it?
Are you learning anything new at the moment (not English? How long have you been learning it?
Do you have a special hobby? How long / you / do it?
Do you have a special hobby? How long have you done it?
Do you go to a gym? How long /you / be a member?
Do you go to a gym? How long have you been a member?
Do you live in a house or in a flat? How long / you / live there?
Do you live in a house or in a flat? How long have you lived there? / How long have you been living there?
Are you on Instagram or another social network? How long / you / be there?
Are you on Instagram or another social network? How long have you been there?
Do you give money to, or do you work for, a charity or NGO? How long / you / help them?
Do you give money to, or do you work for, a charity or NGO? How long have you helped them?How long have you been helping them?
Do you do any sport or exercise? How long / you / do it?
Do hyou do any sport or exercise? How long have you done it? / How long have you been doing it?
What gadgets (e.g. e-reader, smartphone, etc.) do you have? How long / you / have them?
What gadgets (e.g. e-reader, smartphone, etc.) do you have? How long have you had them?
Is there a TV programme or series you regularly watch? How long / you / watch it?
Is there a TV programme or series you regularly watch? How long have you watched it? / How long have you been watching it?
Where do you work or study? How long / you/ work or study there?
Where do you work or study? How long have you worked or studied there? / How long have you been working or studying there?