Press and hold simultaneously for about 5–8 seconds until the update screen appears.
This is the safest method for fixing "soft-bricked" or boot-looping devices using official Huawei software. Get the Official HiSuite on your PC. nova 5t flash file fix
If you have the official firmware (Stock ROM) files, you can flash them without a PC using a USB drive. Press and hold simultaneously for about 5–8 seconds