There are several HowTo's like this one
or this one
that you can follow to reset a lost root password. Basically, you have to edit the /etc/shadow file and remove the characters between the first and second colons, save the file.
Can I try to reinstall the OS from a USB stick?
You could, although you will learn more by trying to fix the problems.
Or is the SSD corrupt in some way?
No way of knowing for sure. I do know early production SSD's had a limited write life. So it could be a hardware failure.
I don't use Suse, so I don't know if it uses Grub or Grub2, they are quite different. Treat this as a learning exercise, try to edit the shadow file, with the aid of the instructions. Ask questions if you get stuck.
BTW, welcome to the forum.