If you start from scratch on the live-usb:
su
cryptsetup luksOpen /dev/nvme0n1p6 nvme0n1p6_crypt
mount /dev/mapper/nvme0n1p6_crypt /mnt
mount /dev/nvme0n1p4 /mnt/boot/efi
manjaro-chroot /mnt
when you’re finished, unmount in this order:
umount /mnt/boot/efi
umount /mnt