how to change save button to Save and keep published? In the content form want to change the  publish checkbox and save button into the dropdown "Save and keep published" and Save and unpublish
How can i change the layout for all content type.
This looks like you want to change the node edit form back to the old layout of Drupal 8.3. You can use this module:

https://www.drupal.org/project/publishing_dropbutton