Hi there.
When I am in a shop buying a pen, can I say: I am buying a pen.
I mean I want to express I am doing this action of buying. But I know "buy" is an instantaneous verb, and we can't use the instantaneous verb to make a progressive tense. So I'm not sure if the sentence "I am buying a pen" is correct.
I'm looking forward to your reply. Thank you very much!