To be English or not to be English?

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Across
  1. 3. Its synonym is comprehensible
  2. 6. All over the world
  3. 8. Germanic tribes
  4. 9. A native English speaker
  5. 11. Its opposite is useless
  6. 12. Momolingual is its opposite
Down
  1. 1. Its synonym is global
  2. 2. To improve
  3. 4. Simplified English
  4. 5. A mixture of two languages
  5. 7. A local language
  6. 10. Its opposite is unofficial