Hello and welcome!
To guide you to a solution we need some substantial data. Please boot with your Manjaro install device and chroot into you system.
Open a terminal and type:
manjaro-chroot -a
Now you are on your local installation within this terminal.
Now type these commands (each line is one command):
inxi -Fxxxa --no-host
lsblk
cat /etc/fstab
journalctl -b -0
Copy and paste it here like here described:
If the output is cut with “>” on the right side, then please expand the window of the terminal or CTRL + - for decreasing the font size and CTRL + + for increasing.
Thank you