Fix typos and grammatical errors

[Dimitrolito]

What ❔

This PR addresses several typos and grammatical inconsistencies across the documentation:

1. Fixed article usage errors: Corrected "a array" to "an array", "an changing" to "a changing", and "an unique" to "a unique".
2. Removed duplicated word: Fixed "also also" to "also".

Why ❔

• Improves the clarity and professionalism of the documentation.
• Aligns the text with standard English grammar rules for better readability.

---

Checklist

• PR title corresponds to the body of PR.
• Documentation errors have been reviewed and corrected.
• No functionality is affected; these changes are purely editorial.

---

Notes

This PR ensures that the documentation is more accessible to readers, avoiding potential confusion caused by grammatical mistakes or typos.