This isn't Arrow... But ok, did you do this steps for flash?
- Flash stock Android 9, flash the twrp given in the post
- Boot to stock, skipping WiFi, Google login, check VoLTE is ok (if you have it).
- Go to twrp, wipe, then click format data in wipe menu, write 'yes', enter.
- Install ROM and any add-ons you need