How to Disable Gutenberg and Keep the Classic Editor in WordPress
Firstly let's explain what GutenBerg is:
Gutenberg is WordPress editor with a goal to modernize the WordPress writing experience.
Gutenberg is the default WordPress editor with the release of WordPress 5.0.
How to disable it:
First thing you need to do is install and activate the Classic Editor plugin.
The plugin works out of the box, and it will disable the Gutenberg editor upon activation.
This plugin also gives you an option to keep both Gutenberg and the Classic editor at the same time. You can configure this in the plugin’s settings.
Don’t forget to click on the save changes button to store your settings.
You will now be able to see a new link under the Posts menu to create new posts using the classic editor.
I've done this because my used WordPress theme wasn't ready for the change and it completly messed up the website. Couldn't edit or add new posts because of that. So this was for me the only possible way to change that fact.
I hope this post will help you resolve the issue fast.