I apologize for my immature behaviors.

我为我的幼稚行为道歉。

He is an immature boy rather than a man.

他是一个发育未全的男孩，而不是一个男人。

He blurted out some immature words.

他脱口而出了一些不成熟的话。

Stop being so silly and immature, Chris!

别这么愚蠢和不成熟了 克里斯

She is emotionally immature.

她在情感上不成熟。

He said that we were emotionally immature.

他说我们在感情上是不成熟的。

His speech is immature, his vocabulary limited.

他讲话不成熟，词汇量也有限。

He was a young fellow, very green, very immature.

他是个年轻的家伙，没什么经验，很不成熟。

She's just being childish and immature.

她真是小孩子气，太冒失了。