"El gato duerme entre los perros."
Translation:The cat sleeps among the dogs.
Continuous is easy. Start with "estar" conjugated into whoever is doing something, and take a verb and replace the ar/er/ir at the end with "ando" for -ar verbs and "iendo" for -er/-ir verbs. For example, "Yo estoy cantando" means "I am singing", and "Yo estoy comiendo" means "I am eating".
@CookEmily - re: ...among dogs
You almost got it perfect. The only mistake is the missing definite article "the" in front of dogs. This particular "the" conveys that the dogs that are mentioned in the sentence are some specific dogs, as opposed to just any dogs in general.
In the case of the time and space constraints placed on Duo, we are not privy to any information contained in the context which a sentence like this may have been lifted from or the situation where the circumstances may have compelled someone to form this simple declarative thought (with or without the expectation of actually speaking it.)
So for us, the articles in the sentence give us very important hints as to what the circumstances may be. But alas, we just have to take them as they are granted to us and make sure to include them in our translations.
I'll capitalize article in question in the spanish version of the exercise sentence so that you can see it more clearly. It is the definite masculine plural article that is just before and agrees with "perros".
El gato duerme entre LOS perros.