Put on top of everything

Hello…I’m working on a new website

And i need that the button “prenota” must be on top of everything

here is the error:

https://ibb.co/VTBfdc4

I use also a custom CSS code to fix the position of the button and i also use the z-index but…something wrong, here is the code

#floating { position: fixed; right: 0; top: 20%;
width:15%;
border-radius:5px;
background-color: #79bd3a;
z-index: 1 !important;
}