Free shipping and payment and cash on delivery

Hey there,
i can’t find a way to set correctly shipping methods and payments in woocommerce:
1. when a customer reach a certain amount on my website (30 euros) is able to have free shipping (I was able to hide other shipping methods using PHP), but when the customer wants to purchase by cash on delivery – the system doesn’t let me have that kind of payment (and shows just paypal).
-If i want to pay cash on delivery and i have “free shipping” it just lets me pay with paypal.

2- right now it’s possible to have the option of cash and delivery just by purchasing under 30 euros.

3. when a customer gets free shipping should be able to pay just a part of the cash on delivery taxes (due to the fact that the shipping is free).

Used this snippet for hiding other form of shipping when reached the free shipping amount:

// Hide shipping rates when free shipping is available.
/**
 * Hide shipping rates when free shipping is available.
 *
 * @param array $rates Array of rates found for the package.
 * @return array
 */
function my_hide_shipping_when_free_is_available( $rates ) {
	$free = array();

	foreach ( $rates as $rate_id => $rate ) {
		if ( 'free_shipping' === $rate->method_id ) {
			$free[ $rate_id ] = $rate;
			break;
		}
	}

	return ! empty( $free ) ? $free : $rates;
}

Please help me out! I’m stuck and having some issues with customers. Thanks

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