Change his/her text in other language in BuddyBoss platform activity when someone update his/her activity

functions.php

/**
 * This will translate the string
 */
function child_theme_slug_setup() {
	load_child_theme_textdomain( 'buddyboss-theme-child', get_stylesheet_directory() . '/languages' );
}

add_action( 'after_setup_theme', 'child_theme_slug_setup' );

/**
 * Change his.her text in other language
 *
 * @param $action
 * @param $activity
 *
 * @return string
 */
function bp_xprofile_format_activity_action_updated_profile_callback( $action, $activity ) {
	$profile_link = trailingslashit( bp_core_get_user_domain( $activity->user_id ) . bp_get_profile_slug() );

	$text = bp_get_user_gender_pronoun_type( $activity->user_id );

	if ( 'his' == $text ) {
		$text = __( 'his', 'buddyboss-theme-child' );
	} elseif ( 'her' == $text ) {
		$text = __( 'her', 'buddyboss-theme-child' );
	}

	$action = sprintf( __( '%1$s updated %2$s profile', 'buddyboss' ), '<a href="' . $profile_link . '">' . bp_core_get_user_displayname( $activity->user_id ) . '</a>', $text );

	return $action;
}

add_filter( 'bp_xprofile_format_activity_action_updated_profile', 'bp_xprofile_format_activity_action_updated_profile_callback', 20, 2 );

Reference Link: https://localise.biz/wordpress/plugin/beginners