"I do not want bread."
Translation:Я не хочу хлеб.
хочу хлеб ‧ Accusative Case - Direct Object ‧ Whenever a verb, like "read", "cut" or "want" acts directly on some noun, the latter is a Direct Object. Such Nouns take the Accusative case. ‧ ‧ www.duolingo.com/skill/ru/Accusative-Case%3A-the-direct-object/tips-and-notes ‧
I think so, yes. But inanimate masculine nouns (things) take the nominative form in the accusative case. Only animate masculine nouns (living beings) change to genitive.
According to russian people, when the negative is used, you can use genitive or accusative. Both are correct, however the use of genitive case is more common.
Is the я necessary or can they infer it from the conjugation and just say не хочу?
Technically, yes, you need the Я. As it is explained to me, a two year old throwing a temper tantrum might leave it out, but in regular speech – especially as an adult – you would keep it in.
Why I have to write "khocu khleb" instead of "hocu hleb"? That "k" doesn't make any sense...