I cannot remember my Apple id

On your iPhone logged into iCloud… Settings > Apple ID > the Apple ID is near the top of the display.

The suggestions from Apple:

If you forgot your Apple ID password - Apple Support

If you forgot your Apple ID - Apple Support

How to use account recovery when you can’t reset your Apple ID password - Apple Support

Contact Apple for help with Apple ID account security - Apple Support

If this is Activation Lock, the email address is shown as a hint. And id this is an iPhone purchased used, these questions can be involving lost or stolen iPhone or iPad devices and fraudulent sales. Such devices are not going to be useful.

Hello ~ You're signed in here on an Apple ID. Take a look here for further information:

If you forget your Apple ID or password

~Katana-San~