“当我看完这封信，我偷偷地笑了”求助这句话的英文翻译

楼上全部不对。看完信怎么可以用when来引导? 显然是受中文的误解。

偷偷笑，smile in silence

翻译：after I finish this letter, I smiled in silence

when i finished reading this letter, a indistinguishable smile comes over my face.

When i read the letter,i smile in my heart.

There is a simle on my face after reading this letter.

When I read the letter, I secretly smiled.