in short:
lsblk -f to find the needed partitions
sudo cryptsetup open /dev/name_of_partition encrypted to open the encrypted container
sudo mount /dev/mapper/encrypted /mnt to mount the / file system to /mnt
don’t forget to mount the EFI partition if you have an EFI system
sudo mount /dev/sdxY /mnt/boot/efi as an example in that case
manjaro-chroot /mnt /bin/bash to chroot
no sudo needed anymore once inside chroot - you are root - be careful
exit to exit chroot when finished