Looks fabulous. I've just a few minor suggestions. :D
2. Several rows of flats were built to solve the housing problem.
==> But in America--going back to your previous post about "at"--'apartments were built' would be the norm. :wink:
4. A flash of lightning lit the sky followed by a loud roar of thunder; a large quantity of water began to fall.
==> The underlined portion sound odd.
5. Several sheets of paper fluttered to the floor as a gust of wind blew through the window.
==> Typo. the, not he.
6. A group of people gathered round the scene of the accident. There was a stain of blood on the road beside the overturned car.
==> I'd use around or 'round. :D
9. The audience stood up as the head of Ministers filed into the conference room.
==> Tdol'll catch this. I'm Canadian, and so, 'head of Ministers' sounds odd to me. We don't pay that much attention to politics. We trust too much. :D It's a British term, right?
All the best, :D