Translation:Which is mine?
3rd person possessive suffix.
Hangimiz? = lit. our which? → Which one of us?
Hanginiz? = lit. your which? → Which one of you?
Hangisi? = lit. their which? → Which one of them? or simple Which one?
I thought it would be : benim hangisi? as long as the question word usually comes at the end of the sentence. is this case an exception?
the question word doesn't come at the end of the sentence, the question word is placed where the object would normally be placed: Bu benim: This is mine. Hangisi benim? Which one is mine?
only "mi" question words, answering yes/no questions are placed at the end.
"benim hangisi" is completely wrong, although you can say "benimki hangisi" - you learn more about this in the -ki skill.
and that works with neredesin when it is placed in the end of the sentence. because it is placed in the object: "sen neredesin?". "*ben pastanedeyim".
Hm, when I asked the question, I was thinking that "I am" would be translated as "benim" [because "-im" and its variants are the suffixes meaning "I am", like in "Öğretmenim"], but now I realize that "benim" is only the possessive form "my", and nothing else. I guess you can't even translate "I am" directly without making it sound weird (if it's possible at all).
So I'm surer now that it should be "Hangisi ben?" or something similar.
'Benim' means both 'my' and 'I am'(ben-im(1st singular person marker)).
Furthermore, you must use person marker. So there are two ways you can say 'Which one am I?': 'Hangisi benim?' or 'Ben hangisiyim?'
There is no such thing as 'Hangin benim?'. 'Hangisi benim?' is in fact shorter version of 'Onların(Bunların/Şunların/...) hangisi benim?' since 'onların' can be omitted.