呢句咩意思？點解用否定完成式又加時間詞

意思是：我不是認識了 Mark 很長時間

1 － 為什麼用否定完成式？
如果不用，意思就會是「我認識了 Mark 很長時間」，完全相反了啦。

2 － 為什麼加時間詞？
也是意思上的原因。
你可能問 very long 前面不是要加 for 嗎？沒錯是要加的，加了會清楚些，不過很多時為了簡潔會省略了 for，就如這句一樣。

2014-05-07 15:22:44 補充：
至於用完成式的原因，是因為想表達「了」的意思，比較：
現在式：I do not know Mark very long （我不是認識 Mark 很長時間）
完成式：I have not known Mark very long （我不是認識了 Mark 很長時間）
哪句自然些，一目了然吧。

"香港地道"廣東話係話，我識得阿麥唔係好耐咋。

2014-05-07 23:51:34 補充：
example:

Idiomatic English:
I do not think it will rain. (instead of "I think it will not rain")

中文地道語:
我認為不會下雨。

2014-05-08 01:01:15 補充：
Idiomatic English again:

Positive sentence:
I have known Mark (for) a very long time. ("for" is optional)

(instead of "I have known Mark (for) very long.")

Negative sentence:
I haven't known Mark (for) very long.
(meaning: I knew him only a short time ago.)

2014-05-08 01:45:53 補充：
But, if you say,
"I haven't known Mark (for) a very long time,"

you would give a meaning of
"it is a very long time since the last time I knew Mark."

I have not known Mark very long

I have not known Mark a very long time.

同樣解作: 我不是認識了Mark 很久.

從以前到現在的一種行為, 時間延續下keep 住做. 就用 have + Verb (+en / ed)

廣東話係話，我唔係識得阿麥好耐架。