The omission of words is often ovvurs frequently in Japanese when the elements
which can be understood from the context. And this makes harder for the
learners to understand who is the subject, object or the other elements.
However, Japanese doesn't sound natural without omitting.
o-namae (wa nan desu ka) (What's) your name? anata wa (donata desu ka.)(Who are) you? doko kara (kimashita ka)Where (are you) from? piitaa-san no(denwa bangoo )wa (nan-ban desu ka)?piitaa-san no(denwa bangoo )wa (nan desu ka)? anatano(iimeeru adoresu)wa (nandesuka)(What is) your (phone number)?