I'm at a loss for words , How dare you accuse me of stealing .

我真不知道该说什么好,你怎么会怀疑是我偷窃呢.

This is the most wonderful gift I've ever received , I'm at a loss for words.

这是我收到的最棒的礼物,我都不知道该说什么好了.

Gosh, that girl is dad gorgeous ,I'm at a loss for words.

天哪,那女孩太美了,我都无法形容了.