Cannot update macOS Mojave 10.14.2 to 10.4.4
Your 512GB HD is a SSD drive right?
APFS works only on SSD drives. (except for the Fusion drives)

The title of your question says: update macOS Mojave 10.14.2 to 10.4.4 => I think you meant 10.14.4 no?
So, do you really need your system to have that dual boot thingy?
Otherwise, I would recommend you to wipe you hard drive completely and entirely, but you'll loose everything. (that's why you have your backups up to date :-) I hope)
Once your drive is empty, start the installation of macOS Mojave from a USB thumb drive?!

Before doing all that, if your system is still working, first create a Bootable USB thumb drive with the macOS Mojave installation on it.

Don't forget that wiping your hard drive will WIPE all your data!