Willem-Siebe

add_filter( 'woocommerce_billing_fields', 'custom_woocommerce_billing_fields' );

function custom_woocommerce_billing_fields( $fields ) {

   // Over-ride a single label
   $fields['billing_first_name']['label'] = 'Your label';
   
   // Over-ride a single required value
   $fields['billing_first_name']['required'] = false;