Stop childishly messing around.

别孩子气般地捣乱。

You should not behave childishly at your age.

在你这个年龄做事不应该孩子气。

Loosen your hands, step into life very childishly.

松开你的手，要极其天真地步入生命。

My daughters have really been acting childishly lately.

最近，我两个女儿都在耍小孩脾气。

It is not just insulting, it's also childishly simplistic.

这不仅带有欺侮性，而且幼稚、简单化。