[hamed]

You can read the explanation and step by step here.  It came up with my first Google search  

https://kb.yoast.com/kb/how-to-install-t...or-plugin/

Basically the Yoast comes with the new standard WordPress Gutenberg Editor.  And with WordPress if you don't like the Gutenberg Editor you can install the classic editor that will disable the Gutenberg Editor and revert back to the old Classic Editor.

Thanks . Does this mean that there are no settings to return to my editor without installing the plugin?
In my opinion, yoastSEO developers should apply this in their settings. Isn't it?
Thanks for your help and the rest of my friends, sorry for creating this thread I was really confused about this.