In English, you say
What are you laughing at? I'm laughing at this situation.
Here, the preposition "at" refers to "this situation" and "what", respectively. In German it's more clear, since the preposition "über" is always before its target:
Über was lachst du? Ich lache über die Situation.
Same in French:
De quoi ris-tu? Je ris de la situation.
In Chinese, the same question would be (according to Duolingo and Google Translate):
To me, this sounds like
You about laugh what? Du über lachst was? Tu de ris quoi?
You laugh about what? Du lachst über was? Tu ris de quoi?
Why is the 在 before the 笑, instead of before the 什么? Is that just "because it is", or am I missing an important point here?