How much longer do you think it will take to finish the repairs?
How much more time do you think you'll need to finish fixing it?
ーHow much longer do you think it will take to finish the repairs?
「修理が終わるのにあとどのくらいかかりますか？」
How much longer do you think it will take to ...? で「あとどのくらいかかると思いますか？」
to finish the repairs で「修理を終える」
ーHow much more time do you think you'll need to finish fixing it?
「修理を終えるのにあとどのくらいの時間が必要だと思いますか？」
How much more time do you think you'll need to ...? で「…するのにあとどのくらいの時間が必要だと思いますか？」
相手を呼ぶ時は Excuse me と言うのが一般的です。
ーExcuse me, how much longer do you think it will take to finish the repairs?
ご参考まで！
How much longer until the repair is done? 「あとどのくらい長く（How much longer）修理が終わるまで（until the repair is done）かかりますか？」という意味です。
How soon can you finish the repair? How soon は「どれくらい早く」という意味です。
カナダ 
アメリカ合衆国 
