Do u think sabo realy died back then in chapter 588?

cuz i'm not realy sure

he mets dragon talkes with him
and just when he says it would be nice to be the captain of such a great ship he gets blown in to peaces...

does it make sence that Oda, Eiichiro intodruce a new charater just to let him die?

Yes, if that character was meant to develop other characters to what they are in present time. Reference Nami's Bel Mere.

u mean like he influence luffy and ace so much to what they are now
thats why he created him?