How can I delete standard fields?

You can do this by adding following code in your theme functions.php

add_filter( "adverts_form_load", "my_adverts_form_remove_fields" );
function my_adverts_form_remove_fields( $form ) {
    if($form["name"] != "advert") {
        return $form;
    }

    $to_remove = array("adverts_price", "adverts_account", "adverts_phone", "adverts_category", "adverts_location");

    foreach($form["field"] as $k => $field) {
        if(in_array($field["name"], $to_remove)) {
            unset($form["field"][$k]);
        }
    }

    return $form;
}

just customize the $to_remove array to remove only the fields you do not want to use.