Help for update Huawei Ascend G7 L01 to Android 5

Hi.
I bought Ascend G7 L01 few days ago.
And when i turn it on i get an 29 mb update, and after update that i search for update and no new updates!
So, i want update that to android 5.
This is my phone info:
Android 4.4.4
Build Number G7-L01V100R001C00B270
Custom Version CUSTC185D001

I need a safe method to update my phone.
I appreciate that if anyone show me a safe method to update my phone.
I read lots of ways to update it but i get little confused about Build Number and Custom Version and i don't know which firmware is work on my phone.

Thanks.