How can I open my phone when I forgot the password

Here is what you need to do if you have forgot your Apple ID Password:

If you forgot your Apple ID password - Apple Support

If you forgot your passcode, you have 2 options. This one may be used if you know your Apple ID Password:

If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support

If you are not able to use that method to reset the passcode, you will need a computer and have to follow these steps:

If you forgot your iPhone passcode - Apple Support