"His father died last year."
Translation:Onun babası geçen yıl öldü.
we simply don't use locative here, similar to english actually. for last year, next week, tomorrow, etc you don't need a preposition - and no suffix in Turkish
this doesn't work. "son yıl" means "the last year of something", but not "last year". As in "Üniversitenin son yılı güzeldi- The last year of university was nice". Is it clear?
I think they're asking what the SI means at the end of babası. I'd like to know too.
It is the 3rd person possessive suffix. "baba" is father. "babası" is "his/her/its father"