How to update Huawei g6-u10 KitKat (rooted) to a higher versions ?

[Esadienema]

This has been exhausting and I don't know much about how to do it.

I have unlocked and rooted my huawei g6-u10 and I want to install a new version of android but I have no idea how can I do it or where to find the files I need.

I have heard about custom ROMs and unofficial versions.
Do I need them ?