ではないと思う

I don't think ...

→ だ
phrase Uncommon #14,013
I don't think ... Used to politely or cautiously express that something is not the case. Literally, it means “think it is not”; the negative usually sounds more natural in English as “I don't think ...”.
JA: これは正しい答えではないと思う。
EN: I don't think this is the correct answer.

彼は中国人ではないと思う

I don't think he's Chinese.

トム億万長者ではないと思うんだ

I don't think Tom is a billionaire.

私は実際それほどフランス語が得意ではないと思う

I don't actually think I'm that good at French.

そうするのは賢明ではないと思う

I don't think it's wise to do that.

彼女の話真実ではないと思う

I don't think what she says is true.

彼の言うことは本当ではないと思う

I don't think what he says is true.

彼は大したミュージシャンではないと思う

I don't think he's much of a musician.

私は彼の話が本当ではないと思う

I don't think what he said is true.

これはいい考えではないと思う

I don't think this is a good idea.