Quote Originally Posted by EGrammar_Learner View Post
I haven't seen them for the last one month.
No. Say:
I haven't seen them for the last month (or "for a month").
Delete one.


Quote Originally Posted by EGrammar_Learner View Post
It is still going on that I have not seen them the whole last month until now. That's why I use present perfect here. Am I right? Thanks.
Simplify! Say:
I haven't seen them for a whole month.
That is present perfect.