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

• [x] 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!)

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[cgarciae]

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