diff --git a/includes/activitypub/collection/class-event-sources.php b/includes/activitypub/collection/class-event-sources.php
index b641f53..feea7fb 100644
--- a/includes/activitypub/collection/class-event-sources.php
+++ b/includes/activitypub/collection/class-event-sources.php
@@ -34,6 +34,8 @@ class Event_Sources {
 		\add_action( 'event_bridge_for_activitypub_unfollow', array( self::class, 'activitypub_unfollow_actor' ), 10, 2 );
 	}
 
+
+
 	/**
 	 * Register the post type used to store the external event sources (i.e., followed ActivityPub actors).
 	 */
diff --git a/includes/activitypub/handler/class-create.php b/includes/activitypub/handler/class-create.php
index d980551..0366259 100644
--- a/includes/activitypub/handler/class-create.php
+++ b/includes/activitypub/handler/class-create.php
@@ -41,7 +41,7 @@ class Create {
 	 * @param int   $user_id  The id of the local blog-user.
 	 */
 	public static function handle_create( $activity, $user_id ) {
-		// We only process activities that are target the application user.
+		// We only process activities that are target to the application user.
 		if ( Actors::APPLICATION_USER_ID !== $user_id ) {
 			return;
 		}
@@ -80,6 +80,8 @@ class Create {
 
 		if ( isset( $json_params['object']['type'] ) && 'Event' === $json_params['object']['type'] ) {
 			$valid = true;
+		} else {
+			return $valid;
 		}
 
 		if ( empty( $json_params['type'] ) ) {
@@ -87,7 +89,7 @@ class Create {
 		}
 
 		if (
-			'Create' !== $json_params['type'] ||
+			'Create' !== $json_params['type'] || 'Update' !== $json_params['type'] ||
 			is_wp_error( $request )
 		) {
 			return $valid;
@@ -103,10 +105,22 @@ class Create {
 			'id',
 		);
 
+		// Limit this as a safety measure.
+		add_filter( 'wp_revisions_to_keep', array( 'revisions_to_keep' ) );
+
 		if ( array_intersect( $required, array_keys( $object ) ) !== $required ) {
 			return false;
 		}
 
 		return $valid;
 	}
+
+	/**
+	 * Return the number of revisions to keep.
+	 *
+	 * @return     int   The number of revisions to keep.
+	 */
+	public static function revisions_to_keep() {
+		return 3;
+	}
 }
diff --git a/includes/activitypub/handler/class-update.php b/includes/activitypub/handler/class-update.php
index 12e3c96..a4de6eb 100644
--- a/includes/activitypub/handler/class-update.php
+++ b/includes/activitypub/handler/class-update.php
@@ -10,6 +10,9 @@ namespace Event_Bridge_For_ActivityPub\ActivityPub\Handler;
 use Activitypub\Notification;
 use Activitypub\Collection\Actors;
 use Activitypub\Http;
+use Event_Bridge_For_ActivityPub\Setup;
+
+use function Activitypub\is_activity_public;
 
 /**
  * Handle Update requests.
@@ -21,30 +24,41 @@ class Update {
 	public static function init() {
 		\add_action(
 			'activitypub_inbox_update',
-			array( self::class, 'handle_update' )
+			array( self::class, 'handle_update' ),
+			15,
+			2
 		);
 	}
 
 	/**
 	 * Handle "Follow" requests.
 	 *
-	 * @param array $activity The activity object.
+	 * @param array $activity The activity-object.
+	 * @param int   $user_id  The id of the local blog-user.
 	 */
-	public static function handle_update( $activity ) {
-		if ( ! isset( $activity['object'] ) ) {
+	public static function handle_update( $activity, $user_id ) {
+		// We only process activities that are target the application user.
+		if ( Actors::APPLICATION_USER_ID !== $user_id ) {
 			return;
 		}
 
-		$object = Actors::get_by_resource( $activity['object'] );
-
-		if ( ! $object || is_wp_error( $object ) ) {
-			// If we can not find a actor, we handle the `Update` activity.
+		// Check if Activity is public or not.
+		if ( ! is_activity_public( $activity ) ) {
 			return;
 		}
 
-		// We only expect `Update` activities being answers to follow requests by the application actor.
-		if ( Actors::APPLICATION_USER_ID !== $object->get__id() ) {
+		// Check if an object is set.
+		if ( ! isset( $activity['object']['type'] ) || 'Event' !== $activity['object']['type'] ) {
 			return;
 		}
+
+		$transmogrifier_class = Setup::get_transmogrifier();
+
+		if ( ! $transmogrifier_class ) {
+			return;
+		}
+
+		$transmogrifier = new $transmogrifier_class( $activity['object'] );
+		$transmogrifier->update();
 	}
 }
diff --git a/includes/activitypub/transmogrifier/class-gatherpress.php b/includes/activitypub/transmogrifier/class-gatherpress.php
index 06c196d..1255acd 100644
--- a/includes/activitypub/transmogrifier/class-gatherpress.php
+++ b/includes/activitypub/transmogrifier/class-gatherpress.php
@@ -52,6 +52,15 @@ class GatherPress {
 		$this->activitypub_event = $activitypub_event;
 	}
 
+	/**
+	 * Get post.
+	 */
+	private function get_post_id_from_activitypub_id() {
+		global $wpdb;
+		$id = $this->activitypub_event->get_id();
+		return $wpdb->get_var( $wpdb->prepare( "SELECT ID FROM $wpdb->posts WHERE guid=%s AND post_type=%s", $id, 'gatherpress_event' ) );
+	}
+
 	/**
 	 * Save the ActivityPub event object as GatherPress Event.
 	 */
@@ -64,6 +73,39 @@ class GatherPress {
 				'post_content' => $this->activitypub_event->get_content(),
 				'post_excerpt' => $this->activitypub_event->get_summary(),
 				'post_status'  => 'publish',
+				'guid'         => $this->activitypub_event->get_id(),
+			)
+		);
+
+		if ( ! $post_id || is_wp_error( $post_id ) ) {
+			return;
+		}
+
+		$event  = new \GatherPress\Core\Event( $post_id );
+		$params = array(
+			'datetime_start' => $this->activitypub_event->get_start_time(),
+			'datetime_end'   => $this->activitypub_event->get_end_time(),
+			'timezone'       => $this->activitypub_event->get_timezone(),
+		);
+		$event->save_datetimes( $params );
+	}
+
+	/**
+	 * Save the ActivityPub event object as GatherPress Event.
+	 */
+	public function update() {
+		$post_id = $this->get_post_id_from_activitypub_id();
+
+		// Insert new GatherPress Event post.
+		$post_id = wp_update_post(
+			array(
+				'ID'           => $post_id,
+				'post_title'   => $this->activitypub_event->get_name(),
+				'post_type'    => 'gatherpress_event',
+				'post_content' => $this->activitypub_event->get_content(),
+				'post_excerpt' => $this->activitypub_event->get_summary(),
+				'post_status'  => 'publish',
+				'guid'         => $this->activitypub_event->get_id(),
 			)
 		);
 
diff --git a/includes/admin/class-user-interface.php b/includes/admin/class-user-interface.php
new file mode 100644
index 0000000..b6a9c3e
--- /dev/null
+++ b/includes/admin/class-user-interface.php
@@ -0,0 +1,111 @@
+<?php
+/**
+ * Class responsible for User Interface additions in the Admin UI.
+ *
+ * @package Event_Bridge_For_ActivityPub
+ * @since 1.0.0
+ * @license AGPL-3.0-or-later
+ */
+
+namespace Event_Bridge_For_ActivityPub\Admin;
+
+// Exit if accessed directly.
+defined( 'ABSPATH' ) || exit; // @codeCoverageIgnore
+
+use Event_Bridge_For_ActivityPub\Integrations\Event_Plugin;
+
+/**
+ * Class responsible for Event Plugin related admin notices.
+ *
+ * Notices for guiding to proper configuration of ActivityPub with event plugins.
+ *
+ * @since 1.0.0
+ */
+class User_Interface {
+	/**
+	 * Init.
+	 */
+	public static function init() {
+		\add_filter( 'page_row_actions', array( self::class, 'row_actions' ), 10, 2 );
+		\add_filter( 'post_row_actions', array( self::class, 'row_actions' ), 10, 2 );
+		\add_action(
+			'admin_init',
+			\add_filter(
+				'map_meta_cap',
+				array( self::class, 'disable_editing_for_external_events' ),
+				10,
+				4
+			)
+		);
+	}
+
+	/**
+	 * Add an column that shows the origin of an external event.
+	 *
+	 * @param array $columns The current columns.
+	 * @return array
+	 */
+	public static function add_origin_column( $columns ) {
+		// Add a new column after the title column.
+		$columns['activitypub_origin'] = __( 'ActivityPub origin', 'event-bridge-for-activitypub' );
+		return $columns;
+	}
+
+	/**
+	 * Add a "⁂ Preview" link to the row actions.
+	 *
+	 * @param array    $actions The existing actions.
+	 * @param \WP_Post $post    The post object.
+	 *
+	 * @return array The modified actions.
+	 */
+	public static function row_actions( $actions, $post ) {
+		// check if the post is enabled for ActivityPub.
+		if ( ! self::post_is_external_event_post( $post ) ) {
+			return $actions;
+		}
+
+		$actions['view_origin'] = sprintf(
+			'<a href="%s" target="_blank">%s</a>',
+			\esc_url( $post->guid ),
+			\esc_html__( 'Open original page', 'event-bridge-for-activitypub' )
+		);
+
+		return $actions;
+	}
+
+	/**
+	 * Check if a post is both an event post and external (from ActivityPub federation).
+	 *
+	 * @param WP_Post $post The post.
+	 * @return bool
+	 */
+	private static function post_is_external_event_post( $post ) {
+		if ( 'gatherpress_event' !== $post->post_type ) {
+			return false;
+		}
+		return str_starts_with( $post->guid, 'https://ga.lan' ) ? true : false;
+	}
+
+	/**
+	 * Modify the user capabilities so that nobody can edit external events.
+	 *
+	 * @param array $caps     Concerned user's capabilities.
+	 * @param array $cap      Required primitive capabilities for the requested capability.
+	 * @param array $user_id  The WordPress user ID.
+	 * @param array $args     Additional args.
+	 *
+	 * @return array
+	 */
+	public static function disable_editing_for_external_events( $caps, $cap, $user_id, $args ) {
+		if ( 'edit_post' === $cap && isset( $args[0] ) ) {
+			$post_id = $args[0];
+			$post    = get_post( $post_id );
+			if ( $post && self::post_is_external_event_post( $post ) ) {
+				// Deny editing by returning 'do_not_allow'.
+				return array( 'do_not_allow' );
+			}
+		}
+		return $caps;
+	}
+}
\ No newline at end of file
diff --git a/includes/class-setup.php b/includes/class-setup.php
index b0fd90c..b204bd6 100644
--- a/includes/class-setup.php
+++ b/includes/class-setup.php
@@ -21,6 +21,7 @@ use Event_Bridge_For_ActivityPub\Admin\Event_Plugin_Admin_Notices;
 use Event_Bridge_For_ActivityPub\Admin\General_Admin_Notices;
 use Event_Bridge_For_ActivityPub\Admin\Health_Check;
 use Event_Bridge_For_ActivityPub\Admin\Settings_Page;
+use Event_Bridge_For_ActivityPub\Admin\User_Interface;
 use Event_Bridge_For_ActivityPub\Integrations\Event_Plugin;
 
 require_once ABSPATH . 'wp-admin/includes/plugin.php';
@@ -212,7 +213,8 @@ class Setup {
 
 		if ( get_option( 'event_bridge_for_activitypub_event_sources_active' ) ) {
 			add_action( 'init', array( Event_Sources_Collection::class, 'init' ) );
-			add_action( 'init', array( Handler::class, 'register_handlers' ) );
+			add_action( 'activitypub_register_handlers', array( Handler::class, 'register_handlers' ) );
+			add_action( 'admin_init', array( User_Interface::class, 'init' ) );
 		}
 
 		add_filter( 'activitypub_transformer', array( $this, 'register_activitypub_event_transformer' ), 10, 3 );