"Cows are not cats."
Translation:गायें बिल्लियाँ नहीं होती हैं।
गायें is a feminine noun and the subject being referred to and as a result will be conjugate होना/होनी/होना femininely as होनी
if you're having trouble getting the ल्ल conjunct try the key which is located where the 'd' key normally is on an English keyboard, it makes like a little diacritic that lets you form conjuncts. So you put the first ल, then the ् character, then the next ल, and it produces ल्ल.
I would like to mention that this diacritic is not meant to join letters, instead what it does is strip the default sound of "a" from consonants. As a byproduct of when there is no longer a sound, letters merge, because this is how the script works. Source: Wikipedia article on Devanagari.