It's a computer, and you can't add words into the translation that it's not expecting. "Non è la forchetta dell'uomo." does not have a NO in it. Otherwise it would be "No, non è la forchetta dell'uomo." Funny you should bring up double negatives, because Italian requires them. If you want you say, "I never drive", in Italian it would be "Non mai guido." Litterally, "I not never drive", but to make it good English, you have to change it to either "I never drive" or "I do not ever drive"
- del = di+il (masculine singular)
- dello = di+lo (masculine singular before s+consonant, gn, pn, ps, x, z, i+vowel, y+vowel)
dell'= di+l' (masculine & feminite
singularbefore a vowel)
- della = di+la (feminite singular)
- delle = di+le (feminite plural)
- dei = di+i (masculine plural)
- degli = di+gli (masculine plural before a vowel, s+consonant, gn, pn, ps, x, z, i+vowel, y+vowel)
already knowing french can help translate through the words order, "non e la forchetta dell'uomo" "non est la fourchette de l'homme/la fourchette n'est pas_à l'homme" "not is the fork that man's"/"it's not that man's fork" figure out that word order and you'll be fine from here if you encounter more of them. edit* no idea if it's its proper word order.
Duo usually accepts contractions since they are so common in English. Are you sure you put the apostrophe in? If you are doing it on a phone, did it auto(in)correct to "its"? Also, look at the rest of your translation. Sometimes I think it's not accepting one thing when there was another error in the translation I put in. If it really is not accepting "it's", then it should be reported.
No, it literally means "It is not the fork of the man" A better English translation would be "It's not the man's fork." It is a mechanism for expressing possession. They have possessive pronouns, so if you wanted to say "It's not his fork", you would say, "Non è la sua forcchetta". The "sua" agrees in gender with the noun it's modifying not the person it refers to.
Are you sure? According to this article (http://italian.about.com/library/fare/blfare125a.htm), dell' is used when the noun is singular, masculine, and begins with a vowel.