Whatever you do with your smartphone you do at your own risk and I have nothing to do with the problems with your phone. I have everything working 100% on Android 6.0!
Link download: https://yadi.sk/d/FqJHEE9K3LHGDX
1)Download my archive (flashtool, supersu and twrp + driver)
2) Install the driver from the folder MT65xx USB VCOM DRIVERS - InstallDriver.exe
3)Unpack to any place in the downloaded archive
4) Run Flashtool and a custom the same way:
a) Download-Agent: path to the file MTK_AllInOne_DA.bin
b) Scatter-loading File path to the file MT6750_Android_scatter.txt. It is in the folder TWRP 3.1.0.
c) Check that the tick is only recovery.
d) Click the Download button and connect to usb our off smartphone. Will the firmware be standing by a green checkmark flashtool.
Detachable Usb cable.
5)Download to the microsd UPDATE-SuperSU-v2.65-20151226141550.zip and insert the USB flash drive to a smartphone
Go to twrp. On off mobile hold the keys volume + and the power button and hold until Select Boot Mode, there select Recovery Mode arrow and press volume down to confirm. Next, click Install and ukactive path where the files UPDATE-SuperSU-v2.65-20151226141550.zip and install it. After rebooting and enjoy our Root!