Explanation:
its shows how memories are sometimes good or sad
Schaffer mistakenly told his assistant to strike alarm Box 342, and as a result, firefighters were directed to an incorrect location during the Chicago fire of 1871.
This is the best example of adding concrete details. It specifically says which alarm box Schaffer told his assistant. The original sentence makes it seem as the miscommunication was the big problem. While it was a problem, the fact that the firefighters went to the incorrect location is really the reason the Chicago fire of 1871 was so devastating. Including these details makes the writing much clearer and easier for the reader to follow.
Timothy was so vain that the very first thing he did every morning was to look at himself in the mirror for five minutes.
It looks good.
You did a nice job being descriptive and your grammar looks fine.