If for sure you have forgotten your primary mail, for as far as I know, there's no guaranteed way of knowing the mail, you should rather prefer bypassing the lock instead of trying to get to remember the mail, here:
At the very beginning from the Welcome panel choose appropriate language.
Afterwards connect your device to one of the available wifi networks.From the Verifying your account panel active the keyboard to input the email.
In the next step press and hold the icon from the left-down corner of keyboard.
As soon as Huawei Swype menu appears on the screen choose the Help.
After that tap Version and the select Swype.
From the text in front of you click the first link and choose Browser.
You can now use the Internet browser. Type in the following phrase in the searcher: download.hardreset.info
Next choose Huawei folder and download Huawei Bypass Google file.
Open the menu of the browser by tapping the Middle key.
Then select Download options.
In the next step open the Bypass application.
When the Install blocked screen appears on the screen choose Unblock.
Afterwards tap Install and accept necessary conditions.
Tap Open icon and Cancel for the Delete installation package.
Excellent! You are right now in the Main screen of your phone.From the main menu choose Settings .
In the next step tap Backup & Reset and select Factory data reset.
Then choose Reset phone, and confirm the whole operation tapping Reset phone again.
Good job! Wait to accomplish the process! This operation removes your Factory Restet Protection.
If incase you switched to another input method. Hard reset the phone again as below:
First of all, hold down the Power key in order to turn off the device.
Next, press and hold the Volume Up + Power button at the same time for a few seconds.
Let go of held keys as soon as the Huawei logo appears on the screen.Then select by using Volume buttons option "wipe data/factory reset", and confirm that with Power button.
Once more choose "wipe data/factory reset" from the menu, and accept it with Power key.
When the Recovery Menu pops up accept option "reboot system now" by using Power button.
Congratulations! You have just performed the hard reset operation
Boot it up and try again the previous procedure to bypass the verification