It’s hard to know for sure from internet search, but some sources say it is sweet potato leaves. They don’t quite look like sweet potato leaves to me, but I am not a plant person So I thought to ask the community here in case someone recognizes it. It is known as gimboa or jimboa in Angola. Here is also a video where someone is showing how to cook them.
Lucky you! Cut, thoroughly wash off any sand grains, slice into big pieces, cook it in a dry tomato - fried fish - sauce with plenty of fried onions, spice with very little ginger, garlics and scotch bonnet towards the end. Serve with steam-boiled green plantains. Voila! Bon appetit!