The procedure is not without risk. Therefore as a first step I strongly recommend to store the EFS¹ of your H850 via TWRP, e.g. on an external SD card or the cloud or your PC.
The EFS¹ (Encrypting File System) file system contains all “important” data about device code (IMEI), security zone, product code, serial number and MAC addresses for Bluetooth and WLAN. All hash values of the system files are also stored there.
As so often there is not only one way back to stockROM.
Do you want the StockROM with TWRP and Bootloader to remain open
the complete StockROM and Bootloader to be (again) locked (Oem Lock)?