Is my sentence correct?

Please help me. It's urgent

Anonymous The man [who] I've been waiting told me he wouldn't be able to come.

You need an article and punctuation.
The "who" is optional. Year ago, it would have had to be "whom." Few people would say that now.

It feels a little unfinished.
The man I've been waiting for has just told me he isn't be

Anonymous Is my sentence correct?

No. I think you want this: The man I've been waiting for just told me he [won't be able to come / can't make it].

can't make it is more casual.

CJ