I have turned on the volume to the highest level, yet I still can't hear anything.

Try charging the device indoors with the power off. If the device still won't charge, the device may need new cables to charge. Consider purchasing a micro USB to USB cable and a USB to wall adapter. If new cables are not helping, then the device may need a new battery. Check out the troubleshooting guide on this device for more information: TomTom GO 500 Troubleshooting Guide

This problem may be caused by a faulty digitizer. Try tapping various parts of the screen. If the device is only registering commands at certain parts of the screen, registering incorrect commands, or not registering at all, then the digitizer may need to be replaced. If the device's screen is cracked, then this problem may not be caused by a faulty digitizer. A cracked screen may indent the structure of the device and unintentionally apply pressure to the digitizer. To overcome this pressure, the digitizer will need hard taps. Normally, the digitizer will respond to soft taps. Replacing the screen may fix this problem. Check out the troubleshooting guide on this device for more information: TomTom GO 500 Troubleshooting Guide