If you know the username of the account but don't have the password you can recover your Google account by using the recovery email or the recovery phone number, but if in case you don't have access to your recovery email and phone as well you will be able to recover your Google account and reset the password by answering the security questions which you setup at the time of account creation.
If you want Google account recovery by answering the security questions you need to follow the instruction given below:
Go to Google account recovery page
Enter your username or the phone number relevant to the Google account you want to recover
Click on next
It will ask you for the password and there you need to click on Forgot password
It will prompt to use the recovery phone number for the verification
Click on I don't have access to this phone
It will prompt to send the verification or password reset link on your alternate (recovery) email address
Click on I don't have access to this email
It will prompt to answer the security questions
Click on OK
Answer the security questions correctly
It will prompt to reset the password of the Google account
You need to enter the new password and then confirm the password click on done
Once you are done with the password reset you are already logged in and you can use the new password to login to your account in future.
