hello i made new account how i can delete old??

Hello ~ Are you the original owner ? Is there a message displayed? Perhaps the iPhone is activation locked. Take a look here:

Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Also:

The All Too Common SAD Reality of Buying a Used iPad/iPhone

If this is not your issue post back with more details.

~Katana-San~

hello i made new account how i can delete old??

how to delete account

See this Apple article: Sign in with your Apple ID

Sign in with your Apple ID - Apple Support

👉 use one Apple ID to access all Apple services and make all of your devices work together seamlessly. 

FYI -> You can't merge multiple account.

Have you forgotten your Apple ID?, check your Apple ID via your email box, see this Apple article: If you forgot your Apple ID

If you forgot your Apple ID email address or phone number - Apple Support

OR see -> Having trouble signing in?

https://iforgot.apple.com/password/verify/appleid

Then see this Apple article: What to do after you change your Apple ID or password

What to do after you change your Apple ID or password - Apple Support