"Where is he from? - I do not know."
Translation:Звідки він? - Я не знаю.
Is it always necessary to include the personal pronoun in a sentence, even when the verb already tells you the person? Is only "ya ne znayu" correct, or should "ne znayu" work aswell?
"Не знаю" is OK in this case, but sounds very colloquial. Usually, personal pronouns cannot be omitted in Ukrainian and it is better to use them always until you have enough experience.