Don't worry this is no more needed!
Before following this procedure make sure to back up everything you want to save because we gonna wipe data partition!
Edit the twrp files are slightly modified to suite honor 8 pros partition layout. As they where originally for mate 9 it had to be done.
1.backup everything you want to save on your internal storage.
2. Download https://mega.nz/#F!mwJVAaaR!Nh_NZ8jCmp76VGVWC-WPbg and extract it on your external storage.
3. Extract magisk-root.zip and flash twrp-magisk-H8P.img using fastboot using this command: fastboot flash recovery_ramdisk twrp-magisk-H8P.img
4. Flash fstab-decrypt.zip which will replace fstab in vendor/etc/
5. FORMAT DATA in twrp.
6. (optional) boot system and set everything up.
7. Reboot to recovery and flash Magisk.zip
8. Wait and see
Open Magisk manager settings
Press update channel > custom and enter
You'll get latest Magisk for huawei devices
Credits firedance1961 at www.android-hilfe.de for providing files.
TopJohnwu for magisk
This has been tested on both EMUI 8.0 and AOSP treble build and works fine!