How root huawei y7 trt lx1/ switch slot? I am trying to root my phone, 


I unlocked bootloader
I have uploaded Magisk-v16.6 to internal storage
I flashed by many twrp versions (fastboot flash recovery TWRP_3.2.3_TRT-LX1_by_kiruha_21.img/ twrp-3.2.3-4-land /
boot-without-enciphering-data / twrp-3.3.1-0-CRO_U00 /
TRT-TWRP-3.1.1-0818 /TWRP_3.2.2_TREBLE_TRT-LX1_by_kiruha_21 /
twrp-3.3.1-0-whyred but every time when I start phone i twrp mode -
touchscreen not working 
I read https://forum.xda-developers.com/showpost.php?p=77597383&amp;postcount=86


And I try to switch slot but when I run fastboot --set-active=a
I get error: Device does not support slots.
and when I run fastboot getvar current-slot I get 

current-slot:
finished. total time: 0.002s

my fastboot version fastboot version 1:8.1.0+r23-5~18.04
The bootloader must load the DTBO image that is compatible with the recovery image. in your case Touch is not working because the TWRP version does not support it. There is not much you can do, the TWRP kernel must be compiled with touch support (or maybe binary hex-patched).  

Look for dtbo.img or (edit: dtb is appended to kernel for y7)
use the adb shell commands TWRP comes with:
https://twrp.me/faq/openrecoveryscript.html  

You can also try to boot TWRP from fastboot instead of flashing it, sometimes this will affect to touch screen work.  

fastboot boot C:\adb\TWRP_3.2.2_TRT-LX1_by_kiruha_21.img


regarding switch slots, you can not switch if you don't have A/B device. don't mix up different recoveries.  

please note the differences between /etc/recovery.fstab

only in TWRP_3.2.2_TRT-LX1_by_kiruha_21

/dev/block/bootdevice/by-name/userdata fs: f2fs  
/dev/block/bootdevice/by-name/  
vendor, product, version, log  


only in TWRP_3.2.2_TREBLE_TRT-LX1_by_kiruha_21

/dev/block/bootdevice/by-name/userdata fs: ext4  
/dev/block/bootdevice/by-name/  
fsc, lksecapp, sbl1, dip, dpo, limits, mcfg, mdtp, mota, oem, syscfg  


Please check if your phone has f2fs or ext4 file system, and check if vendor partition is present or not. Select the proper TWRP variant according to your partition layout.  

you can check your partitions from adb shell or terminal emulator (one of these commands will work)  

ls -d /dev/block/*/*/*/by-name/*
ls -d /dev/block/*/*/by-name/*
ls -d /dev/block/*/by-name/*


for file system type (one of these commands will work)

df -t ext4 /data
df -t f2fs /data
df -T /data
mount | grep "/data "