So guys it's been a while and guess wat i found a solution how you can install mac os high sierra or even mojave,so i had this problem that i could not install anything other than sierra because i was missing firmware partition even mojave would not work so here is a bypass you can do to install the newest version :
what you'll need :
usb drive (32gb) , 16 gb won't work.
vmware fusion
carbon copy cloner
1 :First install vmware fusion on a working mac or on a mac you want to install a new version (High sierra or mojava)
2 :Download the (high sierra or mojave app from mac app store don't open the app. close it
3 :Create a new vmware machine using the (high sierra or mojave app) (select installation file)
wait for it to fully install.
4 :Download carbon copy cloner on you're vmware fusion (high sierra or mojave ) machine
open and select to copy you're virtual machine into a usb drive or external ssd (hhd)
when it's done cloning it will ask to create a recovery partition on the usb accept and wait for it to finish.
5 :After it's all done shutdown the virtual machine and boot from you're usb (external device).
6: (IMPORTANT) If you want to install it on you're internal drive or any other hhd or sdd do this
Open carbon copy cloner and select usb as source and you're device as destination.
after it's done again it will ask to create recovery partition accept it again and you are done
THIS WORKED FOR ME IF ANYTHING HAPPENS TO YOU'RE MAC IT IS NOT MY RESPONSIBILITY.
You have a working mac os (Mojave or High sierra on a external hhd or ssd )
