Hi @ana_731 and welcome to the Manjaro forum.
If you cannot login to the system either directly or via TTY – Use the Terminal / TTY – then you will need an alternate method such as a bootable Manjaro installer, Live installer, or possibly the Super Grub2 Disk. The Restore the GRUB Bootloader link is the recommended guide to follow.
Regarding the major parts of your problem, I’m afraid I’m unable to assist (I never use encryption; deferring to a secure network environment, instead). I suggest you wait for better advice than the average forum user might give.
I’ll try to encourage some of that for you. @Yochanan .
Cheers.