This problem did not occur when using manjaro xfce. but after i switched to kde i started to see this. How can I skip this step? I know my passphrase. And when i write my passphrase (same time my login password) manjaro opens. And I have to retype my password.
Attempting to decrypt master key…
Enter passphrase for hd0,msdos1 (some numbers bla bla)
Welcome to the forum! 
Please edit your topic title and post to tell us what this is.
Please see:
If you encrypted your install with LUKS then you have to bla bla your password.
If you want to autologin in KDE Plasma then go to Settings > Startup and Shutdown > Login Screen and down the window click on Behavior
Then enable Automatically log in
i changed the title, thanks for warning.
Thanks for your help. How to decrypt my disk permanently and basically?
… not possible
you can’t “decrypt” it in place
back up your personal files if there are any
and reinstall unencrypted
then restore your personal files
… Why would you choose to encrypt your system
(lock the door with a key)
when you know that you do not want to use a key - or even unlock the door - to get in? 
what a bad luck 
it’s not that bad
it usually takes just ~30 minutes to do a fresh installation
… unencrypted, this time
There seems to be a cryptsetup-reencrypt --decrypt option, but better just reinstall dm-crypt/Device encryption - ArchWiki
