NumPy’s official website is

NumPy reference pdf has everything about NumPy. Currently, it is over 600 pages.

I listed a few tutorials below. Note that it is ordered beginner to advanced.

In this 30 min. video, Jake Vanderplas is explaining what is NumPy and why it is being used for data science.

From Python to Numpy by Nicholas Rougier is an excellent book/website of NumPy.