根據我所知道的，estáis 適用於第二人稱複數，而且後面的形容詞也是複數型，
這裡是不是應該翻成 “為什麼你們這麼傷心?”
shouldn’t this be in the Spanish learning section ?
Maybe, but since his post was in Chinese (excepting the picture), I can see why he posted it here, too.
Tagging @xia.fan, since she speaks Chinese.
Gosh! It’s hard to report a mistake on this app!
I’ve emailed the staffs about this and they gave me http://community.memrise.com/c/language-quarters this link. And I managed to find this forum especially for Chinese speaking users because I supposed the Spanish courses for Chinese speakers were created by native Chinese speakers. Am I wrong again?
Does anyone know how should I report translation mistakes?
Sorry, I didn’t read your whole post. Like this: @xia.fan you mean?
No, you’re fine 
I tagged xia.fan because she’s the one on the Memrise team who speaks Chinese, so I’m hoping she can help you deal with this.
If your English is good enough (and it seems like it is), then it might be better for this thread to be moved to one of the two Spanish forums, since the course that you’re talking about it is for learning Spanish. That’s something that the mods would need to do, though, so it might be better to just wait until xia.fan swings by this thread.
And yes, sadly, it’s difficult to report mistakes from the app :\
Now that xia.fan has found this thread I moved it to its section. Chinese speaking people will be able to express themselves in English or Chinese here.
@sircemloud, IMHO, it would be better to start a new topic for this course-forum. As it is, I think that if someone looking to report an error with the course visits this topic, they’re going to be very confused.