決めなくて

not decide

→ 決める
決め decide, determine + なく Negative (adverbial form) + Te-form (conjunctive)
verb Rare #41,087
not decide Negative te-form of 決める; often used with いい to mean “not have to decide.”
JA: まだ決めなくていいです。
EN: You don't have to decide yet.
Conjugation of 決める
Past
Present
決めて決めなくて
Desiderative
Indicative past
Conditional
Indicative present
Indicative

先ず第一に名前を決めなくて

First of all, we have to decide on a name.

どの順番入る決めなくていいですか

Do we not need to decide what order to enter in?

— 親切なクムジャさん (2005)

自分のことは自分で決めなくてはいけない

You have to make your own decisions.

でも決めなくてもいいのよ

But you don't have to decide now.

— アイム・スティル・ヒア (2024)