If you really like how the WordPress page and post layout use to be and prefer not to use the new layout in the update 5.0, there is an easy option for you.

You can simply install the Classic Editor plugin and once it is activated your page and post layout will revert to the way it was before the 5.0 update.

To install the Classic Editor plugin, go to plugins - add new and place classic editor in search bar. I have indicated the Classic Editor plugin below. Install and then activate.

If you would like to chop and change between the old style and the 5.0 block style layout, just deactivate and activate the Classic Editor plugin as desired.