について詳しく

in detail about; knowledgeable about

→ に
phrase Rare #29,361
in detail about; knowledgeable about With verbs such as 話す, 説明する, and 調査する, it means doing something in detail about a topic. With 詳しい or 詳しくない, it describes being knowledgeable or not knowledgeable about something.
JA: その問題について詳しく調べました。
EN: I researched that issue in detail.

ご提案について詳しく説明してください

Please explain your proposal in detail.

我々はその事故の原因影響について詳しく調査する必要がある

We need to thoroughly investigate the causes and effects of the accident.

自分で運転しないので、彼はについて詳しくない

Since he doesn't drive himself, he doesn't know much about cars.