Can't resize partition.

So I upgraded from Big Sur to Monterey and made a separate partition for it so I don't lose any data if it goes backwards now I'm in Monterey but I cannot add the remaining space to my Monterey disk. I also cannot format my other partition yet because it still contains all my files. Migration assistant won't work either because the Monterey Partition is too small.

Here's a screenshot of it, I can only make my old Big Sur partition larger.