I know this question has already been somewhat addressed earlier (I'll quote the comments here), but I didn't find the answer very clarifying. So I'll repeat the issue, quote the explanations that were given, and attempt to explain why I'm still confused.
In a test question, we are asked:
How would you say ''I haven't been in France for long.'' ?
The only tenable-seeming answers are:
-Je ne suis pas arrivé en France depuis longtemps (marked correct)
-Je n'arrive pas en France depuis longtemps (marked incorrect)
In spite of the questionable use of the verb "arriver", I actually chose the latter option on the basis that, in the lesson, we are told:
– Ne ... pas + Passé composé + depuis longtemps = not for a long time / not in ages -> It's over and done in the past
– Ne ... pas + Présent indicatif + depuis longtemps = not long / not for long -> It started a short while ago, and is still ongoing
Commenting on the issue, Cécile's gives this transition:
– I haven't been in France for long = Je ne suis pas en France depuis longtemps.
Like the instructions in the lesson, and the second answer in the quiz (which was marked incorrect), this translation conforms with the use of the Présent indicatif + depuis longtemps to describe something that "is still ongoing."
Chris, however, gives two translations:
Je ne suis pas en France depuis longtemps.
Je ne suis pas arrivé en France depuis longtemps.
He then explains "The former sentence talks about a period which started in the past and continues up until the present time. The second one focuses on the event of the arrival, which has no connection to the present."
For me personally, this explanation is too terse and opaque to clarify anything. It fails to explain what focusing on "the event of the arrival" changes in terms of grammar rules. Further, it doesn't acknowledge, in this instance at least, the fact that the lesson's instructions are seemingly contravened, or explain why this is so.
Either there is a mistake in the quiz (which is doubtful), or another section needs to be added to the lesson to explain this exception.