Contact form HTML, Returning a "Success" text in the .html file

i have this question and i can't find a solution. I'm pretty new in the programming. So..

my HTML file with the form is contact.html (straight html file)

The php code is in separated file. So, everythings work fine, but.. I want to have the return text for the "success" or "fail" in the in my html file (let's say under the submit button). Is it possible if it's not php file with html code, but straight html. And can you tell me what should I do?

I hope you understand me.