"You have the half."
Translation:Du hast die Hälfte.
In response to the question "why is the object first in 'Die Hälfte hast du'". In English we indicate what is a subject or what is an object by where it sits in the sentence. Thus you cannot say in English 'The postman bites the dog' to mean that the dog bites the postman. In German however, you can tell what is an object or a subject by whether it is in the nominative or accusative, therefore they are able to be more flexible in the ordering of their subjects and objects in sentences. 'Du hast die Hälfte' is the same as 'Die Hälfte hast du" 'Der Mann isst den Apfel" is the same as "Den Apfel isst der Mann" because the "den" before the apple tells you that the apple is the object, and thus the thing being acted upon. Similarly, the "der" before the Mann indicates that the man is the thing doing the eating. Naturally context can also help.
It's not wrong. Both forms is valid. Once it's made clear that "du" is the subject (if it were the object it would be "dich", and the verb would be "hat") and therefore the object is "die Hälfte", it doesn't matter whether the object is at the beginning or the end of the sentence.