Hi,
Check in Windows device manager whether you can see your phone as a preloader com port device after connecting to USB. It is recommended to use Windows 10 for flashing.
However, before doing that, I would need to back up my user data... and res ...
No, please don't try to backup and restore the old user data. Back up your files on an external storage, cloud or SD card if you have one installed in your phone, then just reinstall all your previous apps.