1.Go to Settings and About Phone and tab 7 time on the Build Number to unlock the Developer Options
2.Go back and go into Developer Option and enable Oem Unlock.
3.Go to the Website and Unlock your Bootloader https://emui.huawei.com/en/plugin/unlock/index(Warning,this delete all your Data,Backup your Data!!!)
4.Reboot into Bootloader and unlock it with: fastboot oem unlock your generated Code
5.Download Twrp Supersu and ADB Minimal.
6.Copy the Twrp in the Adb Folder and Supersu2.82 in External SD Card
7.Reboot again into Bootloader and Plug in the Phone into the PC.
8.Open the Adb folder and Doupleclick the cmd-here.exe and Type:fastboot flash recovery twrp_Honor_7x.img and after flashing Type fastboot reboot.
9.After rebooting Power off the Phone and wait 5-10sec.
10.Press Volume up and Power Button at same time to boot into Twrp and flash Supersu2.82,after flashing swipe to right wipe Dalvik Cache and reboot.
11.The Phone Reboots 2 times this is normal you have root and Twrp installed.
I am on L21C432B101 and works perfekt
Sorry for my Bad English.