Subtotal cart variable php

I found something like this, be it doesn’t seem to work..

$session_cart = $woocommerce->session->cart;
	if(count($session_cart) > 0) {
		$total = 0;
		foreach($session_cart as $cart_product)
			$total = $total + $cart_product['line_subtotal'];
	}

To be clear, I want to use following rules:
When you chose to pick up to items: extra fee = 0
When you chose to deliver the items:
– Amount (subtotal before discount) is below €250:
– between 1 – 6 items: extra fee = 8,7
– between 7 – 12 items: extra fee = 10,6
– …
– Amount (subtotal before discount) is above €250: extra fee = 0

I have following code:

add_action('woocommerce_cart_calculate_fees' , 'add_custom_fees');
function add_custom_fees( WC_Cart $cart ){
	$fees = 0;
	$aantal_items = 0;
	$min_order = 250.00;

	$country_shipping = WC()->countries->countries[ $order->shipping_country ];
	$country = $country_shipping[0];

	$chosen_methods = WC()->session->get( 'chosen_shipping_methods' );
	$chosen_shipping = $chosen_methods[0];

	foreach( $cart->get_cart() as $item ){
	$aantal_items = $aantal_items + $item['quantity'];
	}

	$session_cart = $woocommerce->session->cart;
	if(count($session_cart) > 0) {
		$total = 0;
		foreach($session_cart as $cart_product)
			$total = $total + $cart_product['line_subtotal'];
	}

//PICKUP
     if ($chosen_shipping == 'local_pickup') {$fees = 0;}
//DELIVERY
     elseif ($chosen_shipping == 'woocommerce_flatrate_percountry') {

if ($total < $min_order and $aantal_items >= 1 and $aantal_items <= 6) {$fees = 8.7;}
elseif ($total < $min_order and $aantal_items >= 7 and $aantal_items <= 12) {$fees = 10.6;}
elseif ($total < $min_order and $aantal_items >= 13 and $aantal_items <= 18) {$fees = 11.8;}
elseif ($total < $min_order and $aantal_items >= 19 and $aantal_items <= 24) {$fees = 20.5;}
elseif ($total < $min_order and $aantal_items >= 25 and $aantal_items <= 30) {$fees = 22.4;}
elseif ($total < $min_order and $aantal_items >= 31 and $aantal_items <= 36) {$fees = 23.6;}
elseif ($total < $min_order and $aantal_items >= 37 and $aantal_items <= 42) {$fees = 32.3;}
elseif ($total < $min_order and $aantal_items >= 43 and $aantal_items <= 48) {$fees = 34.2;}
elseif ($total < $min_order and $aantal_items >= 49 and $aantal_items <= 54) {$fees = 35.4;}
elseif ($total >= $min_order) {$fees = 0;}
else {$fees = 60;}

	 }

        $cart->add_fee( 'Verpakkingskosten', $fees);
    }

WC()->cart->subtotal_ex_tax;