<div class="product-section__information_quantity">
    <input name="count_product" type="text" value="50">
    <input name="count_product" type="text" value="1000">
    <button class="click">click</button>
</div>

var allCountInform  =  0;

$(document).ready(() => {
  $(document).on('click', '.click', function () {
    allCountInform  =  0;
    $(this).closest('.product-section__information_quantity').find("input[name=count_product]").each( function () {            
      allCountInform  = allCountInform+parseInt($(this).val());
    });
    alert(allCountInform);
  });
});