I don't want two container disks - trying to delete

I have brought a second hand MacBook Air 2015, running on macOS Catalina. Only just realised there are two container disks, and so I have run out of space on my primary disk (Macintosh HD - disk 1).

I have been trying to delete Container disk 2, or disk 1, or merge them. I have tried in recovery mode also but it says both disks are not mounted. Not in recovery mode, when trying to delete, it is greyed out for disk 2 and not for 1. But I still get an error message when I try and delete disk 1. I don't want to add further partitions, I created "KateNZ" in the hope this would fix my issue, and to test out what I can do. But it hasn't helped or solved the issue.

I don't mind which one goes, its a new Mac with not much on it, just want to be able to access all the storage space and not have this set up as it is complicated and unnecessary for me. Thank you