終えなければ

if ... don't finish

→ 終える
終え finish, complete + なけれ Negative conditional + Conditional (if/when)
verb · conditional Rare #38,195
if ... don't finish Often used in the expression 〜なければならない, meaning “must ...”.
JA: 今日中に仕事を終えなければ、帰れません。
EN: If I don't finish the work by today, I can't go home.
Conjugation of 終える
Conditional
終えたら終えなければ

明日までにパーティーの準備終えなければなりません

I have to finish preparing for the party by tomorrow.

この仕事を終えなければ次の契約をとることはできない

If I don't finish this job, I won't be able to get the next contract.

どんなに疲れていようとも今日君はその仕事を終えなければいけない

No matter how tired you are, you have to finish that work today.

わたしは夕食前に宿題を終えなければなりません

I have to finish my homework before dinner.