Yeah, you have 2 vdevs. One is a mirrored vdev, the other is a single disk.
You've made some serious mistakes.
First, you need to backup your data, pronto.
Now, here's the 2 mistakes I see.
1. You didn't create the pool from the GUI. If you are like most people you did it from the CLI and you shouldn't have.
2. Instead of replacing a failed disk you added the disk as its own vdev.
For #1, the only fix is to replace disks and hope you have enough space(statistically you might not have enough space unless you disable swap.. which isn't recommended but you have no choice)
For #2, the fix is to either destroy the pool or add another disk to the single-disk vdev thereby making it a mirror. (You will have to do this from the CLI because the GUI doesn't support this). You cannot remove a disk once its been added as a vdev.
Good luck!
Edit: If, at any point, your single disk vdev fails, you will lose the pool. This is why its imperative for you to make a backup.