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Friends,

I'm Brazilian. What I know about Present Perfect is:

1) Actions that started at a time in the past and still happen today:
Ex.: I have lived in NYC since 2005.
Obs.: In these cases, it is better to use Present Perfect Continuous, right?

2) Actions that happened at a time in the past, but we don't mention "when":
Ex.: I have studied Japanese once.
Obs.: If we mention "when", we use Past Simple:
Ex.: I studied Japanese last year.

3) Actions that have just happened:
Ex.: I have just arrived.

4) Actions that happened at a time in the past and bring consequences to the present:
Ex.: I am late because I have missed the train.

Is that correct? Well, I guess so because I've seen this in a grammar book.

Well, what I want to know is... Sometimes, watching movies, I notice that they don't use Present Perfect in some situations they should. I mean, of course they use it, but it's very common to hear Past Simple instead of Present Perfect in some situations in which the last one should be used. Is it that common with native speakers? I mean, just like double negatives or questions without auxiliary verbs? Is it part of native speakers' quick spoken language, although it is incorrect?

Thanks for your time.

brunces
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Brunces1) Actions that started at a time in the past and still happen today:
Ex.: I have lived in NYC since 2005.
Obs.: In these cases, it is better to use Present Perfect Continuous, right?
Not necessarily. The Non-Continuous is often just as good.

And note that some verbs do not allow the continuous form.

I have known him since 2005. (Good.)
I have been knowing him since 2005. (Wrong!)

CJ
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Sometimes, watching movies, I notice that they don't use Present Perfect in some situations they should. I mean, of course they use it, but it's very common to hear Past Simple instead of Present Perfect in some situations in which the last one should be used. Is it that common with native speakers? I mean, just like double negatives or questions without auxiliary verbs? Is it part of native speakers' quick spoken language, although it is incorrect?
.

Sometimes there are options, as in your #4:

I am late because I have missed the train.-- This would be said by cellphone, standing on the platform as the caboose disappears down the track.

I am late because I missed the train.-- This would be said upon arrival at the office.

And sometimes there are regional differences:

AmE: I already had breakfast, thank you.
BrE: I've already had breakfast, thank you.

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Comments  
Many native speakers, such as myself, don't always use correct grammar. This is because we understand what the person means. That's why you will often find grammatical errors in an English-speaking country. Just think about it: it means your English is better than the natives'!
 CalifJim's reply was promoted to an answer.
Bruncesit's very common to hear Past Simple instead of Present Perfect in some situations in which the last one should be used.
There may be specific reasons for using the Past Simple other than sloppiness. I would have to see the specific example before I decided.

CJ
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 Mister Micawber's reply was promoted to an answer.