I have been debating with my wife (she is American) over the correct use of each phrase. She doesn't know anything about grammar and also grew up with a lot of immigrants so she suggested I just post and ask.
When and how should I use each phrase apart form the grammatical guidelines of a specific/unspecific time?
For example could one be more polite/rude or do they suggest something else, e.g. the person was waiting all day or just for a few minutes?
Could I say 'What were you doing last week' because I'm interested in what they were doing or should I say what have you been doing last week to sound more polite which in turn would contradict the rule of not using a specific time with 'have been' since 'last week' is a specific time, or should I ask 'What did you do last week?'