How can I correct a word on the CKEditor field?
According to AdamPS in Enable browsers' (native) spell checker in CKEditor


  2) If you browser supports spelling suggestions, the way to access
  them in Drupal is slightly different. When you are in an edit area,
  then the normal browser context menu may be replaced by the editing
  context menu. However you can access the browser menu by clicking
  Control. [But on a Mac it is potentially command and on a tablet
  ....??]


You need to hold down CTRL before right clicking. (which worked for me on Windows OS)



An alternative would be to install the SpellCheckAsYouType(SCAYT) plugin for CKEDITOR 




  Note: You have to build a custom module to install CKeditor plugins in
  D8.