Before looking for a replacement, first thing I would do is turn off the phone, wait a few seconds and restart it. You may also want to thoroughly clean the screen or remove the screen protector if you have one.
If your device's internal storage is full, this can cause slow screen response, so try freeing up some space. If this doesn't solve it, enter Safe mode to find out if a recently installed app is causing the issue: the procedure is documented in the user manual (p.155), you can also download it from the manufacturer's website.
Other things you could try: look out for abnormal memory consumption by certain apps, install a touchscreen calibration app to increase accuracy or run diagnostic software to detect faulty parts