$wpdb->query($wpdb->prepare

$update = $wpdb->query($wpdb->prepare(
                        "UPDATE immobilien
                        SET
                        'title'     => $title,
                        'zipcode' => $zipcode,
                        'city'  => $city,
                        'street'   => $street,
                        'object_art' => $object_art,
                        'expose_img_count'    => $expose_img_count,
                        'added' => $added,
                        'processed'    => $processed,
                        'purchase_price'    => $purchase_price,
                        'rental_price'    => $rental_price,
                        'room'  => $room,
                        'bedroom'    => 2,
                        'bathroom'    => 2,
                        'living_area'   => $living_area,
                        'usable_area'   => $usable_area,
                        'construction_year'    => $construction_year,
                        'energy_pass'    => $energy_pass,
                        'buyer_prov'    => $buyer_prov,
                        'object_categorie'    => $object_categorie,
                        'description'    => $description,
                        'img_path_list' => $img_path_list,
                        'land_area'     => $land_area,
                        'free_at'          => $free_at,
                        'power_consumption' => $power_consumption,
                        'energy_efficiency_support' => $energy_efficiency_support
                        WHERE online_number = $online_number"
                    ));