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What can I do to make my sentences better?

1) It is too expensive and problematic to take security for major events to the next level.
2) Due to the increased danger of terrorism, security must be strengthened significantly.
3) For large events, thousands of security guards need to be hired, and the price is extremely high.
4) Also, keeping security is easier said than done because a large number of security guards are not well-trained.
5) That is why the safety of the local people also goes down.