hound is a correct tranlation for Hund
No, it's not, at least not reliably. Not accepting "hound" is a deliberate decision by the course contributors, because in today's English, "hound" most often refers to "one of any of several breeds of dogs trained to pursue game either by sight or by scent, especially one with a long face and large drooping ears." (See meaning 1 at https://www.dictionary.com/browse/hound .)
The meaning "any dog" is marked as "informal" there.
See also https://dictionary.cambridge.org/dictionary/learner-english/hound_1 , which only defines it as "a dog that is used when people hunt animals" or https://www.oxfordlearnersdictionaries.com/definition/english/hound_1?q=hound , which says that a hound is "a dog that can run fast and has a good sense of smell, used for hunting". Those two do not even mention the meaning "any dog".
Compare also a Google Images search for "hound" versus "dog".
So accepting "hound" for "Hund" might lead English speakers to conclude that Hund refers specifically to a dog used for hunting, and that a chihuahua (for example) is not a Hund -- when of course it is.