Never pay down a deposit in a bank account until you have met the seller, seen signed a purchase agreement.
No serious private advertisers ask for a down payment before you meet.
Receiving an email with an in-scanned ID does not mean that you have identified the sender. You do this on the spot, when you sign a purchase agreement.
I'm selling a Merida Mission Comp full-suspension bike. The bike is cool, but I finally brought my own. I bought it on kupujemprodajem about a year and a half ago, already modified (the brakes were replaced with disc brakes and a different rear shock absorber). I will give a special pump for the rear shock absorber with the bike.