I think you can breed your strter but I dontk now now which answer its good:yes or no,so who can help me?
Yes you certainly can! Most of the starters are in the Monster egg group so can breed with these pokemon:
EDIT: for Platinum, here are the egg groups:
Torterra - Monster + Plant
Infernape - Ground + Humanshape
Empoleon - Ground + Water 1
Egg group list here: http://pokemondb.net/mechanics/breeding
Of course you can, but if you want a baby starter, it must be in the same egg group, and...your starter must be female! you know, the percentage of getting female starter is 12.5%? so, it's hard, but not impossible!
Yea all you need to do is put a ditto and whatever you want to breed and a egg will appear
It will say it on serebii.net egg groups