There’s confusion going on.
p1 is your ESP
p5 is your root partition
Reboot into a live ISO session (from the USB again) to start all over. I fear you’re creating directories redundantly.
After you reboot, setup your mounts like so:
sudo mount /dev/nvme0n1p5 /mnt
sudo mount /dev/nvme0n1p1 /mnt/boot/efi
Now you can use manjaro-chroot -a to enter a chroot session. It is inside of this chroot that you can run the Grub commands.