I think i know what is causing the error but we need to be sure so please execute below commands and post a screenshot of the commands outputs. There are two System partitions we need to delete the one that is not created by us yesterday. This process may take some time to finish.
First of all if you have not we can try Startup Repair (Automatic Repair) tool it can sometimes repair these kind of errors. If you have already use this tool let me know please.