I’m a native speaker and this is difficult to answer! I think like so many things in English it depends on context. Mostly they sound interchangeable to me. I’ve tried to put some explanations below as to how I “feel” they may be used differently - but I’m not a teacher and i’m not sure other native speakers will agree, but this is how I personally would use these: - am working = can be used to talk about a specific instance (e.g. I’m working late tonight) or in general (e.g. I’m often working late in my new job) - work = sounds more general, e.g. - I often work late in my new job. - Do you work late every Friday? - I work late every day Are you going to work late at the office again = sounds like an intention on a specific occasion (e.g. “Are you going to work late in the office tonight or will you be home in time for dinner”)? I’m going to work late tonight = I intend to be at work late tonight I’m working late tonight = 1. I intend to be at work late tonight (exactly same as sentence above). 2. It is night and I am currently at work working late! I hope that is a bit useful, but really you would be perfectly understood whichever one you used and I think even native speakers may disagree over the nuances with these 😁