1: The first thing you want to try is Google’s Account Recovery page. Choose the “I don’t know my password” option and enter your Gmail address, click on Continue.
If you linked a phone number to your Gmail account, you can request a verification code sent in a text message or you can answer security questions under “Verify your identity” section.
2: If you forgot your email address and haven’t set up any recovery information such as a phone number or security questions, you may still be able to find your username in case you have recently used your email account in your web browser. Search your web browser history for Inbox or Gmail® to see if it reveals your address. Technically, your full email address or the first part of it before the character is your username.
3: In case you don’t have access to your recovery email, phone, or other option you may still be able to recover Gmail® password by manually verifying your identity. First thing you need to do is visit the Google Account Recovery page. When there, enter your email address and click “Continue”. Click “I don’t know” option for the password and choose the “Verify your identity” option, which is a really small link under all other available options. Answer all the questions to the best of your knowledge and if you are able to provide the information that is accurate enough you’ll get a successful Google account recovery.