Be absolutely sure you only work on the CLONE, not the actually booted suse! In my fstab there are three partitions mounted on boot, all with the respective UUID of the partition (the “very long number” in your opinion) You have to read fstab AND blkid for the CLONE partition. You can post the output of fdisk -l as a starter. There you will see the boot HDD/SSD as well as the Clone and find out the correct /dev/sdX for your purpose… can you paste the fstab here?