Weird stuff happening on my Acer C720 Mint laptop

I'm in a bit of a rut here.

I went to get some warm clothing and when I came back, my computer had shut off. Weird but maybe it was updating, who knows. Booting it back up (with the legacy boot on a chromebook; i can select which hard drive to boot into) resulted in an errorless message:

With my limited knowledge of the subject I figured that a ninja update had wiped the boot file from it, or the disk was unmounted, whatever. Something that seems easily fixable (and this might still be the case). I made a live USB and did an integrity and memcheck, both of which tued out just fine. Booting into the USB and i run sudo fdisk -l to get the different drives, and my /dev/sda (my 128GB SSD hard drive) displays a couple notable things.

Firstly, my SSD has shrunken from 128GB to 20MB according to fdisk -l, and it also gives me "Disk /dev/sda doesn't contain a valid partition table".

and my live usb being right under it with correct stats, the most notable difference being the size, number of cylinders (1956), sectors, and disk ID. I have no idea what to do at this point, is my data still recoverable? Even if I have to repartition or format my drive, is there any way I can get the data off of it first? Or even better, can I just make it all magically work again?

Any help would be much appreciated!

Edit: After trying to access the PSE109S9 (the other optton being just "file system", apparently 140 TB large [?]) from the live USB, it says that it isn't mounted, but I don't want to touch anything without knowing what I'm doing first. Ill wait for input.