Update nnx_basics.md

[bmucsanyi]

I fixed typos in nnx_basics.md and improved some sentence structures with mild modifications.

What does this PR do?

This PR improves the NNX Basics tutorial by fixing typos and slightly changing commas and sentence boundaries for clarity.

Checklist

• This PR fixes a minor issue (e.g.: typo or small bug) or improves the docs (you can dismiss the other
  checks if that's the case).
• This change is discussed in a Github issue/
  discussion (please add a
  link).
• The documentation and docstrings adhere to the
  documentation guidelines.
• This change includes necessary high-coverage tests.
  (No quality testing = no merge!)

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[cgarciae]

Thanks a lot for doing this @bmucsanyi ! Can you please rebase and resolve the conflicts?