Debugging an existing mobile web pag plus a small task

We are working on an existing website, making web pages to fit for mobile devices. Currently, we met a problem that we cannot solve. The category bar on the webpage, while scrollable on desktops, are not scrollable on mobiles. We believe this is due to a css problem, unfortunately, we are not so good at css so we cannot solve it. So we are seeking for help from css/jquery pros. In addition to that problem, we also need to add a button on the web page, so whenever this button is hit, a seperate screen appears so you can select some filter conditions. Thank you for bidding.