proiect by proiect_featured

// WP_Query arguments
$args = array(
	'post_type'              => array( 'proiect' ),
	'posts_per_page'         => '-1',
	'meta_query'             => array(
		array(
			'key'     => 'proiect_featured',
			'value'   => 'true',
		),
	),
);

// The Query
$query = new WP_Query( $args );

// The Loop
if ( $query->have_posts() ) {
	while ( $query->have_posts() ) {
		$query->the_post();
		// do something
	}
} else {
	// no posts found
}

// Restore original Post Data
wp_reset_postdata();