How can I access my Google account if I forgot the password and do not have the phone number anymore

The whole point of the system is you can't get access if you don't know the password. Make a new account and write the password someplace so you don't lose it. Keep your contact info current and add an email for backup contact.

One trick: get a book on memory improvement at any bookstore and learn the system. Then you can write your birthday as a word and it is fairly certain you are not going to forget that.