Adding storage / working with partitions

// blabber:

I have done as much of my own research and reading and trying as I can til now.
There are 2 drives (well, one hard drive and one ssd) that i fail to make work.
I think its something to do with the mount points?

// what im trying to do:

Using KDE partition manager, i am trying to add 2 drives to my system. One for games and the other for bulk movies and media. What I currently have is one little 120GB ssd that i just installed garuda on; it has the swap, OS and, well, everything else.
After a little looking about I want to use f2fs on the SSD of the 2 drives, and probably exFAT or ZFS for the hard drive. Thats what I have currently, but of course i will probably have to reset them or something.
Strangely, the main SSD (only one in use) right now is named /dev/sdc. Why is it not sda? I never changed it and its the one i installed garuda on.

// what happens and where I need help

I have btrfs and linuxswap on sdc1 and sdc2 respectively- and thats working fine.

sda is the other ssd, and sdb is the harddrive.
i cannot make files, go into them though dolphin and steam does not recognize them as a download path.
sda and sdb are both mounted at /dev/sda /dev/sdb respectively.. i think. when making a filesystem partition (forgive the lack of proper terminology) it says its mounted at "/dev", which is not good. But when selecting a mount point, /dev is not even an option.

what could i be doing wrong?

uh, maybe worth mentioning;
my

lsblk

shows that

sdc1

is mounted at:

/run/timeshift/backup

normal?