I'm not at all clear on the translation or nuance here. Source is a NLPT N1 grammar question.
Confusion #1: The use of に in 「たった三十分のあいだに」. If the translation is "in only thirty minutes", で seems more appropriate, or having no particle at all, based on Difference between 間 and 間に. All answers there indicate that に is NOT optional, and that it indicates a point in time rather than a long period. But the translation "at a point in only thirty minutes" seems like gibberish.
Confusion #2: I'm not clear on the nuance of 「高木の変わり様といったらなかった」. ~といったらなかった implies "very" or "incredibly", but with no other context, how do tall trees "incredibly change"? Their colors changing in the autumn? Their positions moving in a strong wind? I am not sure.