var target = selector_for_element_containing_text ;    // the selector is:  document.querySelector('.audience-info > div:nth-child(1)');
var observer = new MutationObserver(function(mutations) {
  mutations.forEach(function(mutation) {
       modifyElements();
   });
});
var config = { attributes: true, childList: true, characterData: true, subtree: true };
observer.observe(target, config);


function modifyElements(){  // This is just the current code of my script
    // modify element 1
    // modify element 2
    // modify element 3
}