Form fails to run!

hello there! could anyone please help me in my html codes ?
I created a form element which contains username, age, adress, etc. add I set the form method to POST, the action to another html page. but while submitting the form, they just say ERROR, here is my page link :Exemple
thanks to anyone who could help me
my goal is to send form data somewhere where I can see date later

Github pages (which you are using) only allows static pages (GET requests only), you will need different hosting if you intent to use PHP

Also keep in mind that PHP is back-end/server side

For other people reading, here is github repository link/code: GitHub - promoteurpromoteur/exemple