Hi, 'current' means the immediate present; in progress, current events, most recent; up-to-date therefore 'current' and 'present' are interchangeable. Presently is used as an adverb. 'Now' means right at this very moment. Example: Now I am answering your question.

You mean: "presently". "Currently" and "presently" are more precise. "Now" can be a bit abstract. Example: What is your current job = What are you currently doing? "Currently" is used more often than "presently", and is a better choice. "What are you doing now?" is not really a question. It is something used in EFL books because EFL teachers don't really know anything about the English language. Example: 我快走了 = I'm leaving now. If you want to be more specific about the present moment, you say "right now".