My question is about the possiblitiy of going overdrawn by mistake if account is hacked I am new to crypto  currencies and wondered if ones online wallet is hacked and coins stolen could the hacker make you go overdrawn by spending coins you don't have?  Many thanks
You can never spend more coins than a wallet controls, there is no 'overdrawing an account' in bitcoin. You either control the keys that can spend some coins, or you don't.