Whenever I eat lunch with my friend, he always finishes before me.
My friend is always done eating before me whenever we eat lunch together.
この場合、次のような言い方ができますよ。
ーWhenever I eat lunch with my friend, he always finishes before me.
「友達とランチを一緒に食べるといつも彼は僕より先に食べ終わる」
to finish before me で「僕より先に終える」
ーMy friend is always done eating before me whenever we eat lunch together.
「友達と一緒にランチを食べるといつも友達は僕より先に食べ終わる」
to be done eating before me で「僕より先に食べ終わる」
ご参考まで！
Whenever we eat lunch together, he always finishes eating first.
"一緒にランチを食べる時彼はいつも僕より早く食べ終わる"
- Whenever we eat lunch together, he always finishes eating first.
- He always finishes his food faster than me when we eat lunch together.
- He finishes food before me when we eat together.
カナダ 
アメリカ合衆国 
