Unfortunately if you have not registered a secret question which you remember, or an alternate recovery email address or phone number to which you have access to receive a reset code, you cannot prove that you are the account's legitimate owner. Hence account recovery is absolutely impossible and there is no way around it.
Besides, kinda difficult forgetting your phone number dont you think?
Except you registered a gmail account way back in the 2000s... just saying...
Kinda impossible..