Wordpress Ajax & pictures not loading after upgrade to 5.0
I can see the problem (I saw this myself recently), but I don't have a 100% answer.  However, the solution is usually to rebuild your multilingual schema.

This problem is characterized by:


Multilingual mode is activated on your CiviCRM site.
Error in the browser console show files not found at a path with the word "undefined" in it.
Also, "DB Error: no such field" errors (though this can also be caused by missing extensions or failing to upgrade the database after upgrading the CiviCRM files).


Based on these instructions, here's how you rebuild the multilingual schema:

From within CiviCRM (CiviCRM 5.1+ only):


Go to Support menu » Developer » API Explorer.
Set Entity to System and Action to rebuildmultilingualschema.
Press the Execute button.


From the command line (Civi 5.0.1 and earlier):

Drupal 7

drush php-eval 'civicrm_initialize(); CRM_Core_I18n_Schema::rebuildMultilingualSchema(["en_US","fr_CA"], NULL);'

Drupal 8

drush php-eval '\Drupal::service('civicrm')-&gt;initialize(); CRM_Core_I18n_Schema::rebuildMultilingualSchema(["en_US","fr_CA"], NULL);'

WordPress 

wp eval 'civicrm_initialize(); CRM_Core_I18n_Schema::rebuildMultilingualSchema(["en_US","fr_CA"], NULL);'