が到着する前に

before ... arrives

→ が
phrase Rare #35,205
before ... arrives Used to say that something happens before a person or group arrives. The subject marked by が can change depending on the sentence.
JA: 友達が到着する前に、部屋を掃除しました。
EN: I cleaned the room before my friend arrived.

サマンサデイヴィッドが到着する前に食事をテーブルの用意を始めました

Samantha started setting the table before David arrived.

彼は私が到着する前に死んだ

He died before I arrived.

火は消防士が到着する前に隣の建物広がってしまった

The fire had spread to the neighboring building before the firefighters arrived.

事故はが到着する前に起きた

The accident happened before I arrived.