Thanks well I was just going to post and your were faster than me 😀 I made a very silly mistake: instead of this:
$superficie = $group['superficie_o_potencia'];
I should had been:
$superficie = $group['superficie'];
I’m afraid I was too quick assuming things..
Nevertheless, I confirm using get_queried_object does work just fine as well, and may use it in the future, thank you so much!!