What does the first 思う, right after なったら, mean here?
私は大人になったら思う存分ライブに行きたいと思う。
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Sign up to join this communityIt's part of the phrase 思う存分, which means "to one's heart's content'.
The 思う refers the amount/share of something (分) that you think you want to do/have such that you are satisfied.
Alternatively, you could just leave it out and put a に before ライブ.