the customer can't go to the shopping cart. Waiting for a response and nothing happens. Where to dig?

the customer can't go to the shopping cart. Waiting for a response and nothing happens. Where to dig?

Is this via AddToCart Button or Click the Shopping Cart link in the header ?
AddToCart is via Ajax script
Right mouse click on Chrome and Inspect - look for Script Errors
Any errors in the log ?

I'm new to this business. I didn't notice any errors. I copied a piece of code from Chrome.

            $("#small-search-box-form").on("submit", function(event) {
                if ($("#small-searchterms").val() == "") {
                    alert('\u0412\u0432\u0435\u0434\u0438\u0442\u0435 \u043A\u043B\u044E\u0447\u0435\u0432\u043E\u0435 \u0441\u043B\u043E\u0432\u043E \u0434\u043B\u044F \u043F\u043E\u0438\u0441\u043A\u0430');
                    $("#small-searchterms").focus();
                    event.preventDefault();
                }

                window.setLocation('/search?q=' + encodeURIComponent($("#small-searchterms").val().replace(/([ \,\+\-\&\\\|\!\{\}\[\]\^\(\)\"\~\:\;\?\*\/])/g, '\\$1')))
                event.preventDefault();
            });
        

        $(document).ready(function () {
            $('#small-searchterms').autocomplete({
                delay: 500,
                minLength: 3,
            source: function(request, response) {
                $.ajax({
                    url: '/dsearch/',
                    data: "h=dp_suggest&q=" + encodeURIComponent(request.term.replace(/([ \,\+\-\&\\\|\!\{\}\[\]\^\(\)\"\~\:\;\?\*\/])/g, '\\$1')),
                    success: function (data) {
                        var array = [];
                        $(data.SearchProducts)
                            .each(function (e, v) {
                                var object = {
                                    label: v.Name,
                                    manufacturer: v.Manufacturer,
                                    manufacturerPartNumber: v.ManufacturerPartNumber,
                                    value: v.Name.replace(/<em>|<\/em>/gi, ""),
                                    producturl: v.SeName,
                                    productpictureurl: v.ImageUrl,
                                    shortdescription: v.ShortDescription
                                }
                                array.push(object);
                            });
                        response(array);
                    }
                })
            },
            appendTo: '.search-box',
                select: function(event, ui) {
                    $("#searchterms").val(ui.item.value);
                    setLocation(ui.item.producturl);
                    return false;
                }
        })
            .data("ui-autocomplete")._renderItem = function (ul, item) {
                var t = item.label ? item.label : "";
                var z = "";
                var manufacturers = "";
                if (item.manufacturer != null) {
                    manufacturers = item.manufacturer;
                }
                $(manufacturers)
                    .each(function (e, v) {
                        z += v.split("_").pop().replace('+', ' ');
                    });

                var shortdescription = "";
                if (item.shortdescription != null) {
                    shortdescription = item.shortdescription;
                }

                var manufacturerPartNumber = "";
                if (item.manufacturerPartNumber != null) {
                    manufacturerPartNumber = item.manufacturerPartNumber;
                }

                var name = "";
                if (z != "") {
                    name = decodeURIComponent(htmlEncode(z)) + " ";
                }

                if (manufacturerPartNumber != "") {
                    name += htmlEncode(manufacturerPartNumber) + " ";
                }
                //html encode
                name += htmlEncode(t);
                return $("<li></li>")
                    .data("item.autocomplete", item.value)
                    .append("<a><span class='entityType'>" + name + "</span></a>")
                    .appendTo(ul);
            };
                    });
        

in the basket the customer has added a product,click on the basket loading lasts not less than 4 minutes.
this error is returned


Failed to load resource: the server responded with a status of 404 (Not Found) jquery-ui-1.10.3.custom.min.css:1
jquery-migrate-3.0.1.min.js:33 JQMIGRATE: Migrate is installed, version 3.0.1
jquery-ui-1.10.3.custom.min.css:1 Failed to load resource: the server responded with a status of 404 (Not Found)

It's still not clear what you mean by "click on the basket".  Can you describe better, and show a screen capture?