WordPress is deleting font awesome icon tag when accessed from the visual editor

Hi, I have encountered a huge problem with the classic editor. When I am adding font-awesome icons in the “text editor (HTML editor)”, everything works fine. Once I get back to the “Visual editor” the font-awesome code from the text editor “fa-icons” disappears and so are the icons.

Do you know about this problem and if yes, how do I fix it?

Thanks