Before Install macOS Mojave System Update|Must Doing This
macOS Mojave 10.14.3(Update) Installation Guide
After finishing download the update :
Move your all installed kext, System/Library | System/Library/Extension to EFI/efi/clover/kext/other.This is because, if Apple delete your installed .kext during update, after you can't boot.
Apple will not touch EFI/efi/clover/.
After finishing update, you can move .kext EFI/efi/clover/kext/other to System/Library | System/Library/Extension.
After install Update please Don't Restart or Shutdown Laptop/PC:
Check all the kext in System/Library or System/Library/Extension.That .kext extension you have installed.
.kext update required for Mojave
After Updating In Terminal....[if you installed .kext in system disk] if you use EFI/efi/Clover/Kext/Other, then no need this command]
sudo chmod -R 755 /System/Library/Extensions/
sudo chown -R root:wheel /System/Library/Extensions/
sudo touch /System/Library/Extensions && sudo touch /Library/Extensions && sudo kextcache -u /
This is Because, Third party or Unidentified ".kext" extension has to be installed at system/library or system/library/extension. So you need repair permission.
Read Detail in Here<<<
For APFS file system confusion: