HELP: Mac OS Partitions

HELP! So I might have f--- up this time. Basically, I have a 2015 iMac with Mac OS X El Capitan installed, and wanted to try out how Mac OS Monterey ran on that same mac, so I did what I was told to; create a small 50GB disk partition and install there the Monterey. I did that, and worked out great, so decided to give it a chance. Booted back to my Mac OS X El Capitan willing to delete that small partition I did for the test and install the new OS now in the main disk, the one with 950 GB. But there was a problem, Disk Utility wouldn't let me delete that small partition... it didn't even appear in disk utility. So here is where my problem starts: I took the dumb decision to boot back again now in the small partition Monterrey, and delete the 950GB partition with my main OS. The problem? That now I only have an empty container with no OS in there that takes 950GB of my whole storage disk and I can't delete or reallocate the storage of that part of the partition! I'm completely lost and don't know how to solve this. The only thing I want is to have my Mac OS Monterey with my whole 1TB disk, but now I have that 950GB partition blocked or something. Screenshot of my disk utility situation: [https://ibb.co/rf083jFx](https://ibb.co/rf083jFx)