i have been in NY city two weeks ago . i was wondering what is the wrong in this sentence ?

It would work better as:

"I was in New York City two weeks ago."

or

"I have been in New York City."

or

"I have visited New York City in the past."

Sorry I can't tell you the specifics of what is wrong, but you're correct that it's wrong. (By the way the second part of your question should read; "I was wondering what is wrong with this sentence.")

thank you very much !