Strip Drupal Page Template from CiviCRM Contribution Page
You can assign CiviCRM to use the default template in your Drupal theme settings. The default theme doesn't engage your Drupal theme and menu system.

In Drupal 7, it's https://www.example.com/admin/appearance, then scroll down to the bottom of the page and you can set your theme for CiviCRM.



If you want to retain your template but just strip out navigation, you may need to make a new template based on it for CiviCRM to use and assign it.