Other volumes in container macOS Catalina version 10.15.7

Hi!

My Macbook air 2017 is using macOS Catalina version 10.15.7. I have 60,5 GB in other volumes in container (of 121 GB in total) and update to macOS big sur is not possible, because available is only 2,77GB.

The problem has been after we had to do factory reset. I think we did not erase both volume groups (Macintosh HD we erased, but Macintosh HD data was not erased).

Now we can see two Macintosh HD - Data rows in disk utility tool. Can we erase or delete one of those to fix the problem? Should we press the erase button or delete the APFS volume? Or do something else? Is it possible to check somehow that we are not loosing any critical information for running macOS or own data?

How about doing factory reset again? Would it help?

Or can other volumes in container be caused by something else?

Thanks for help!