Why do you think there is a mistake in the second sentence?
If a computer is showing a red line under the word "civilisation," it is because it is using a spelling checker based on US English. "Civilisation" is one of an annoying group of words that are spelled differently in the United States and the United Kingdom.
In the United Kingdom, it is spelled with an s, civilisation.
In the US, it is spelled with a z, civilization.
Because Egypt is closer to England than the US in distance, and because Egypt and England had a long and complicated historical connection, I would guess that when Egyptians use English, they probably prefer to use British spelling, and if a computer system gives you a choice of "US" versus "UK" English, you probably should choose the UK style.
If this is a classroom situation, ask the teacher which kind ot use.
Both countries are used to seeing both kinds of spelling. We hardly notice it. It's almost never a serious error.