How to Backup Your Gmail ID

Login to your gmail id 

Select Personal & Privacy setting

Select Create Archive 

If you wont to backup your all the application (it can take long time to backup)
If you wont to specific backup then select none

Select your specific app 

Select specific labels or all mail labels backup 

 Select Archive type and maximum size

it will take some time or day for backup

you will be get mail from gmail when backup is ready to download

 Download your backup data

Retype your mail password.

You get a mail after some time click it

Download your backup data

you get your data in your selected form like zip .
unzip your data and ...

Your Mail data has been extracted in the MBOX file format:

• MBOX - An mbox is a way of storing mail messages and is supported by common mail clients like Microsoft Outlook 2011, Mozilla Thunderbird, and Apple's Mail program. These files are most easily opened by a dedicated mail client like those listed above.
• Download Mozila Thunderbird and install for same ....   
• https://download.mozilla.org/?product=thunderbird-52.1.1-SSL&os=win&lang=en-US

Enjoy ..... ... ...