I am studying language as communication and I have several doubts.
How many and which acts can an utterance have?
What circumstances do they depend on?
What are the two things that people do when they produce a sentence in the course of a normal communicative activity?
Can anyone advise where to get some information about this.
Thanks in advance for your support.
This looks very like a homework assignment. For many courses, the answer may be to read your course notes. It's surprising how helpful they can be in dealing with questions like these. There may well be a page with the magic number of bullet points, and this is the "right" answer - as far as your lecturer is concerned. Q3 is particularly odd; most people could come up with a list of dozens of "things that people do when they produce a sentence in the course of a normal communicative activity" - promise, vow, undertake, bet, report, narrate, threaten, imitate, ridicule, estimate, approximate, accuse...(perhaps "dozens" is an underestimate - but you get the idea). This is what makes me suspect that your lecturer may have a particular - generalized - answer in mind (based on some recommended resource - such as course notes).
If I'm wrong, Anglika's signposts towards further reading should help.
PS Those things I listed as possible answers for "things that people do when they produce a sentence in the course of a normal communicative activity" were related only to the speech act taking place (some of them would come into the precise definition given here: Speech act - Wikipedia, the free encyclopedia , others wouldn't - as they refer just to 'what's happening' (in a general social sense). I didn't consider the other things people do - either in a physiological sense (they breathe(!), use the muscles of the tongue, and so on) or in a phonological sense (produce vowel/consonant sounds and so on). The question about what happens during an utterance is so vague that I think your lecturer must have some "magic" answer in mind.