I strongly recommend you to check the drive on another PC and with another USB cable. If the issue persists, you should download the drive manufacturer’s diagnostics tool and check the drive for errors. Unfortunately it is highly possible that there is a problem with your drive and that is what causes performance issues. You have tried some useful troubleshooting steps but, sadly, if the drive is damaged, there is not much to do. I presume you have no important data on it, right?
Hope this helps