Those steps that I sent you is to install havoc OS and Resurrection remix. So either one of those ROMs that's how you install it is through those commands after you download the ROM and stick the contents of it in your ADB folder. Before or after that you would then use this thread that we're in right here to download TWRP and you would then use these commands here to get that going..
This gets you into twrp
fastboot boot twrp.img
Or to keep twrp
fastboot flash recovery twrp.img
The only thing that is flashed through twrp is gapps and magisk. The rom you would use what I sent you before.
Progress report:
fastboot flash boot boot.img
Sending 'boot_a' (65536 KB) OKAY [ 1.860s]
Writing 'boot_a' OKAY [ 0.548s]
Finished. Total time: 2.440s
fastboot flash system system.img
Resizing 'system_a' FAILED (remote: '')
fastboot: error: Command failed
What did I screw up? Is the partition too small? I did a "start" or reboot to see if the phone would boot the OS natively, but got "Android Recovery" ... "Your data maybe corrupt...." and 2 choices: "Try again" and "Factory data reset" and it says "Support API: 3" at the bottom.