The best reference I can give you is this Wikipedia page: https://it.wikipedia.org/wiki/Indicativo_imperfetto There is a section that compares the two verb forms. To summarize, you use the "passato prossimo" when the action you are referring about is finished. "ha fatto" means that the subject did it, he or she has already finished, the job is done, we could say. "Imperfetto" can be used for interrupted actions, like: "Ieri studiavo quando il telefono ha suonato" i.e. "Yesterday I was studying when the telephone rang", or two actions taking place in parallel : "Mentre Roberto Benigni girava "La vita è bella", io frequentavo il Liceo", i.e.: "while Roberto Benigni was shooting "La vita è bella", I was in secondary school". Another use is to express an habitual aspect, like: "L'anno scorso leggevo due libri al mese", which means: "Last year I used to read two books a month". Hope it helps, tano

As a rule of thumb (not an invariable rule) passato prossimo refers to something that was done only once, and which had a relatively clear start and finish. If he made one comedy film before that one, it would be "ha fatto" ecc. However this is saying that he made many comedy films, most likely over a period of years. It was therefore a habitual thing and the imperfetto (faceva) would seem to me to be the most appropriate to use.

As a rule of the thumb, 90% of the times you can use "passato prossimo". Unlike English, we use "avere" and "essere" very often. The good news is that you just need to learn "io ho, tu hai, lui ha..." for "avere" and "essere" to speak correctly 90% of the times. Again, it's just a rule of the thumb. Hope it helps.

Roberto Benigni ha fatto molti film comici prima di La Vita e Bella.