i bought a secondhand iphone6 and already reset the phone... it says "cant create apple id? what seems to be the problem? pls help me!!!

Any one device can create only three iCloud accounts (I assume this is what you are trying to do). Once that limit has been reached there is no way round it. You will have to create an iCloud account on another Mac or iOS device (not Windows), then you will be able to sign into it on this phone.

When you say you "reset the phone" do you mean that you have erased all content and settings and returned the phone to its original like new condition?