z-index doesn't work

This is the website: https://panocea.vercel.app/text-editor As you can see, if you open the menu on top, the text of the editor will be on top. I tried fixing it by giving it a z-index: 1 and the popup a z-index: 999 but didn't work. The only that worked was giving the text a z-index of -1 but after doing that I can't focus on the text anymore. Does it work for you? Why isn't it working?

Panocea

Panocea