wysiwyg editor is missing after upgrading to 3.9 version

You can go back to 3.8.3. See http://wordpress.org/download/release-archive/ to find the version you want to roll back to. Then do a manual install – see https://codex.wordpress.org/Updating_WordPress#Manual_Update

Or have your host use a server backup to rollback to.

But please note – 3.9 is the direction WordPress is going – including the updated visual editor. If you’d like to provide feedback on the direction of WordPress, get involved by following and providing feedback as WordPress gets developed here: http://make.wordpress.org/core/.