Drupal 8.x

In an attempt to configure CKEditor, I have disabled it from the default Drupal installation. I want to install again. I believe CDN will be easier. How do I accomplish the following task:

To start using CKEditor 4 on your website, add a single

(http://cdn.ckeditor.com).

If trying to opt for the option of installing on the webhost server,the documentation states:

"Unpack (extract) the downloaded .zip archive to the ckeditor directory in the root of your website."

I am running Drupal v 8.3.7. I notice every day some new illegal generated user accounts, which are locked. I cancel all, but the next day there are again new. Generating new users is permitted only to the only one aministrator, which I am.
Is this a known issue? What can I do to solve this?

I have a drupal 8.3 installed with composer
When i try to update core to 8.4 with : composer update drupal/core --with-dependencies
he told me everythings is up to date.
when i look into composer.json :
"drupal/core": "~8.0",
"drush/drush": "~8.0",

I have drush 8.1.14 installed so i try to changed composer.json with :
"drupal/core": "~8.4",
"drush/drush": "~8.1.14",

then run composer update drupal/core --with-dependencies
but nothing happened, ssh is blocked.

Hello,

I see just after updating the drupal 8.4 readme which tell us to not update width old version of drush.....
So I has an old version and now the site is off....
Fatal error: Interface 'CommerceGuys\Intl\Currency\CurrencyInterface' not found in /home/fournilencevenne/public_html/modules/commerce/modules/price/src/Entity/CurrencyInterface.php on line 16
Drush command terminated abnormally due to an unrecoverable error. [error]
Error: Interface 'CommerceGuys\Intl\Currency\CurrencyInterface' not
found in

If I put in this command in the root file in terminal:
User: rootfile $ drush config-set system.theme default atlas

I get this, apparently commonplace error: