Cannot add gmail account to iOS
As was suggested to you in the comments, you will need to provide more information in order to get some relevant help

Generally speaking the steps to follow are:


Change your password and write it somewhere. I suggest using a password manager.
Login to your google account from your phone with the new password.
Step 2 being a success mean that you indeed changed the password to the one you thing you did.
Add the account in the iOS Mail app and write again the same password carefully in order to avoid any typos.


If 4 failed, it means that you have 2nd factor authentication enabled for you google account.

This means that you will need to generate an application specific password from here and use that as your email password in the iOS Mail app.