Have you searched the forums on xda-developers.com?
I would recommend everyone, the first thing you do to your tablet when you buy it is do a complete backup of all partitions using the easy to use app Macrium Reflect Free. With that you’ll be able to restore any/all partitions and OS’s.
hi, I had a semilar problem with the partition. I have played with ubuntu and have destroyed the partition table. I thought I can use the flash images which can be found here – but the flash way doesn’t work. After one week I’ve found out why: (u)efi + grub. I’ve used the russian images, recommend by user tukull – here http://techtablets.com/forums/topic/heres-how-to-fully-restore-to-factory-win81-bing-android-4-4/