Could anyone explain have + pp in all its..depth?

Here is a comprehensive chart (at the bottom of the page) of all of the English verb tenses.

Perhaps a better example will be “I watched 22 movies yesterday” and “I have watched 22 movies in the past week.” These can both refer to the exact same thing.

The first sentence is in past simple tense. This means that the action (watching 22 movies) occurred at a specific time in the past (yesterday).

The second example is in present perfect tense. This means that all of the actions occurred at an unspecified point in the past, and the actions occurred within a range of time that starts in the past and leads up to the present. The term “perfect” means that the actions are complete. The range of time in this case starts one week ago and leads up to now.

It is also important to point out that if I watched 23 movies in the past week, then “I have watched 22 movies…” is no longer considered true, I would have to say “I have watched 23 movies…”. The information must include all instances of the action in the time range, and the information must be current and up-to-date.

“You forgot” (past simple) means that the person forgot something at a specific point in the past, but does not say anything about what has happened since that point in the past, such as remembering.

“You have forgotten” means that the action occurred sometime in the past, but the time frame leads up to the present. This also means that the person did not remember in the period of time that leads up to the present.

@PhiNotPi Thanks a lot for your accurate and informative answer.
One more question,
then it would be much more likely that the person who has forgotten his respect for me
is still disrespectful to me?
or as it is PERFECT, you do not know if he is but only know the disrespect has just ended?
Oh God this kills me.

It usually means that the person is still disrespectful. The action (of forgetting respect) was completed in the past, but the person is still forgetful.

Some of the complexities of the English tense system are not fully understood by some English speakers. It’s not surprising that many languages don’t even have some of these tenses.

@PhiNotPi
That kind of consoles me, that even native English speakers find this system complex to understand. : – )

@PhiNotPi
Oh please forgive me. Then is it possible that native speakers of English sometimes do not differentiate these two and just don’t bother with the subtlety and mix the uses?
Like…
Have you seen her? and did you see her?
or
Why have you done this? why did you do this?
I don’t see how there can be any difference?

Ah ! While I’m at it,
let me have some other questions solved.
Is there any difference at all between
It’s a good idea doing things this way
and
it’s a good idea to do things this way??
anything at all?

“it is a good idea to do things this way” is correct.

However you can make “Doing things this way” a noun phrase:

Doing things this way is a good thing.

“Forgetting respect” is not idiomatic in English. You can lose respect or feel disrespectful, however.

I can regain your respect.

I regained her respect.

I lost her respect when I put that whoopee cushion on her chair.

If I hadn’t put that whoopee cushion on her chair, I would have regained her respect much sooner.
****************
You make me very aware of what I know intuitively in my own language. You are really amazingly fluent.

Re: “Why have you done this? why did you do this?”

“I don’t see how there can be any difference?”

I’m not sure I do either. I would use them interchangeably.

Another difference between the Simple Past tense and Present Perfect is that the latter is also used to say how many times you’ve done something. I did it yesterday, but I have done it many times.

Thanks everyone, I want to bow to you everyone..

And I am bowing back to you.