Translation:Tomorrow we are going to my sister's house.
"Tomorrow we are going to my sister's home" was marked wrong. (24/07/18) I thought casa means both: house and home ?
What's wrong with 'tomorrow we are going to the house of my sister' ? (other than being awkward wording :p )
I would say it's a bit more than awkward; I doubt it's something many native speakers would say. To put it in perspective, "my sister's house" gets 150 hits in Google, "the house of my sister", 22, and those are mainly in grammar discussions about how English possessives work. The handful of examples in Google Books are mainly from the 19th century:
"Tomorrow we will go to the house of my sister" was my answer incorrectly marked wrong - There should be flexibility in translating sentences provided the correct words and meaning are present.
I think "Tomorrow we go to the house of my sister" should be accepted. It still has the future sense in it.
Five years ago it was pointed out the "head to my sister's house" is an idiom, and that a perfectly acceptable translation is "to go to my sister's house".
Five years later, it's not fixed.
Why do we post bug reports, if not in the hope that future learners will benefit?