I found the solution in the meantime, so the question can be closed. If anyone else is looking for a solution to this, here is how to solve it.
Hide other shipping methods when “Free Shipping” is available
https://woocommerce.com/document/hide-other-shipping-methods-when-free-shipping-is-available/
STEP 1: Go to WooCommerce > System Status > Tools > WooCommerce Transients > Clear transients
STEP 2: Woodmart Child: Theme Functions (functions.php)
Adding PHP code:
/**
* Hide shipping rates when free shipping is available.
* Updated to support WooCommerce 2.6 Shipping Zones.
*
* @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;
}
add_filter( 'woocommerce_package_rates', 'my_hide_shipping_when_free_is_available', <strong>100</strong> );
—————
* “100” in the end == from where delivery is free, eg: 100 euro etc.
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