I have noticed that there are tutorials here, on the first on I have clicked (didn't read them all, just quickly checked one):
There someththing like this quote:
Clear the disk of any existing file systems using random pattern - as the partition will be encrypted this will disguise the partitions and data held on it. It will take some time to complete - hours if you are having a big storage device.
# dd if=/dev/urandom of=/dev/sdy status=progress bs=10M
End of quote.
I don't recommend this at all. It would kill your ssd. I would advise to load live Manjaro KDE and open KDE Partition Manager and remove the junk, e.g. lvm and then do lsblk and sudo wipefs --all /dev/sdx