I wasn't brave enough to use those expressions because I was worried they might be wrong.
I didn't have enough nerve to try those expressions in class because I wasn't sure if they were right or not.
ーI wasn't brave enough to use those expressions because I was worried they might be wrong.
「間違っているかもと不安で、それらの表現を使う勇気がなかった。」
I wasn't brave enough to ... 「…する勇気がなかった」
ーI didn't have enough nerve to try those expressions in class because I wasn't sure if they were right or not.
「それらの表現が正しいかどうかわからなかったので、クラスでそれらを試す勇気がなかった。」
「〜する勇気がなかった」は didn't have enough nerve to ... のようにも言えます。
if they were right or not 「それらが正しいか間違っているか」
ご参考まで!