Here in the below video you will see How to Disable the Gutenberg WordPress Editor.
It makes use of the plugin that allows you to disable the gutenberg editor and you get to use the classic editor. I have seen this to working and I'd recommend you try this method with the classic editor plugin. It should be good enough for you to disable the editor. And you can also use the previously most popular classic editor. It can solve your issues quickly that way.
Do let me know if this advice worked out for you.