to carefully consider the facts of a situation in order to understand something, make a decision, or solve a problem

頭を使う, よく考える
in a very nervous or frustrating state of mind in face of a problem or situation one knows very little or nothing about

手に余る, 自分の手に負えない
said when one does not have a definite answer to a particular question, similar to the questioner

私にもわからない, こっちも見当がつかない
to fail to understand or interpret or understand something correctly

勘違いする, 意味を取り違える
to have no information regarding a particular subject

まったく知らない, 何もわかっていない
used when one is incapable of understanding or remembering a particular thing

どうしても, いくら考えても
someone or something one knows very little or nothing about

まったくわからない存在, 未知の世界
used to describe something that is complicated due to not being clearly described or shown

さっぱりわからない, まったく明確でない
to be incapable of understanding even the simplest concepts

右も左もわからない, 基本中の基本もわからない
the limits of human knowledge or understanding, representing areas that remain unknown or unexplored

未知への最後のフロンティア, 理解の限界点
to become confused, mistaken, or emotionally lost
confused and unable to think clearly

頭がぼんやりしている, 頭が回らない
to fully understand something difficult, complicated, or strange

理解する, 頭で整理する
to make an attempt to understand someone or something that is puzzling

訳が分かる, 話の筋が見える
