'A potentially unsafe operation has been detected in your request to this site' error
This error doesn't come from CiviCRM, but comes from either the Wordfence plugin for WordPress, or your hosting provider has mod_security configured in such a way that it breaks normal operation of CiviCRM.  I generally warn people away from shared hosting providers for this reason and toward a VPS unless they specifically know that CiviCRM is supported.  In theory, a good webhosting company will fix their settings - but bad shared webhosting companies are far more common than good ones!

If you have Wordfence, see if disabling it fixes your problem.  If so, it may be worth exploring a bit further which Wordfence setting is causing the problem.  If you aren't running Wordfence, open a support ticket with your webhosting company.