Mac says password is wrong but it's right. I have to enter it twice to start Mac every time. How could I solve it?
If you are talking about the user password and you are locked out of your mac, you can try the following:


Reboot into the Recovery Drive by choosing the ‘Apple‘ menu > Restart, hold down the ‘command’ + ‘r’ keys on the keyboard during the start up process, when you see the start up screen you can let go. When the machine boots eventually you will see the macOS or OS X Utilities screen.
Go to the Utilites menu and select Terminal
At the prompt type ‘resetpassword’ (hit enter)
Reset your password


Keep in mind that this deletes your keychain, so your saved passwords are lost