A. I have been studying English for one year.
B. I had been studying English for one year.
Could one who hears those sentences argue that "A" case implies "and I am still studying it" whereas "B" case implies "and I am no longer studying it"? If so, how are different in time frame the following sentences?
I worked in Colombia for ten years when the manager sent me to Italy.
I have been working in Colombia for ten years when the manager sent me to Italy.
I had been working in Colombia for ten years when the manager sent me to Italy.
Please, consider that the real situation is that I worked in Colombia from 1963 to 1973 and, for some reason, 1, 2 or 3 must be written today.
However I'm under the impression that only the "3" case is grammatical or, in any case, correct in reference to the real situation, although "1" case seems to be salvageable deleting the preposition "for".
Can anybody explain?