Hello! I am a WordPress developer with experience in Php,HTML,CSS,JavaScript. Infinite scroll in usually achieved by using some plugins which are already there. I don't know if you already have tried those or not, in case you didn't I shall like to try them first, if they don't work I can make you a custom plugin in which will do the exact job by using ajax calls.
Things i shall need is a reference to HTML mark up of your theme.
Word of warning, infinite scroll make footer menu hard to access
Looking forward to hewar from you
Thanks!