What do you call this in English, please? It's something that we use to protect our house.
I'd call it a security gate/grill. They are not common in the UK except on commercial properties, shops etcetera.
I think "gate" as well. A grill would be for cooking food on.
I would use "grille" too. Note the difference in spelling. A "grill" is for cooking. A "grille" is an arrangement of metal slats covering/protecting something.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.