The only way to recover your lost gmail account is by filling out Gmail Recovery Form.
And provide them as much information as as you can. Before filling up this form, please create an additional email account with Gmail. Click the link: https://accounts.google.com/signup
You can fill up the form as given under:
Click the link:
Enter your email address, password, continue OR Choose "I don't know my password".
Enter your email address and click Continue.
Under Enter the last password ***** remember, please choose "I don't know".
And then fill out all of the required details.
Under Contact information, please enter a valid working email address.
Once you fill out all of the required details, Gmail team will get back to you on your alternate working email address in 12-24 hours.
If you have other queries regarding this, please reply back to me the box given below.
And if you can take a second to rate my service(-OK or more -by clicking stars at the top of the page and choose submit), to credit me for my time, work and efforts, that would be greatly appreciated.