i think you posted the different code earlier. But if this is the code you are using right now then you should so this
$slide = new wp_query( array ( 'post_type' => 'banner' ,
'tax_query' =>
array(
array(
'taxonomy' => 'country',
'field' => 'name',
'terms' => 'algeria'
),
),
'meta_query' => array(
'relation' => 'AND',
array('key' => 'page_ads','value' => 'home'),
array('key' => 'position_ads','value' => 'top')
)
));