Translation:Their dumplings are terrible.
Can i say their dumplings taste terrible since nanchi can be translated as terrible tasting?
It is ridiculous to expect us to guess what negative adjective to use here. Why does it have to be "terrible" as opposed to "bad" or "awful" or "lousy" or any of the endless synonyms for "terrible". At the very least, "bad-tasting" should be accepted as a literal translation.
Yes, they need to correct the translation. To just say "terrible" could refer to other qualities, not juste taste.
I would think so.