your hair's length has alot to do with genetics, as well. some people's dna just isn't coded top support long hair, so they'll never have long hair. your hair will grow to it's maximum potential length, and no matter what you do after that, it will stop growing because it's in your genetics. your dna says it won't grow longer, so it won't. there's nothing (aside from extensions) you can do once your hair has reached that length.
same thing with the volume of your hair, it's a genetic thing and there's not much (again, aside from extensions) you can do to fix it.
as has been said, your hair will grow a maximum of 1/2 inch a month. to reach that full 1/2 inch potential, you need to pay attention to your diet. eat things high in protein (ie. eggs, meats) and things high in iron (ie. fruits, vegetables) try to work towards a balanced diet. and especially for the 5 a day fruit sevrings. fruits have alot of vitamins and minerals in them that can help your hair grow strong and healthy. honey is also a good thing to keep in your diet
i also know for a fact that in Russia, there is a very popular remedy for unhealthy hair. it's a mixture of honey, vegetable oil and vodka (i saw you're born in 1987, so you may not be old enough to buy alcohol, i'm not sure what the laws on that are in Bham) so if you can't add in the vodka, definately try the honey/vegetable oil!
there are also some treatments on the market that can help with your hair problems. you might want to see if you can locate any of Dr. Miracle's products where you are, they're pretty amazing! if not, take a trip to your local beauty supply store and ask one of the clerks where you'd be able to find some strengthining/anti-breakage creme
HTH!