How to restart my Galaxy A5 if device appears to be Frozen or not responding?

If your Device freezes or hangs, you may need to close apps or turn off the device and turn it on again. If your device is frozen and unresponsive, press and hold the Power button and the Volume button down simultaneously for more than 7 seconds to restart it.

If after restarting the device, you still find your device freezes sometimes or is sometimes unresponsive, there are some actions you can try to help correct this symptom : 

● You can create some memory space. 
● You can even check for SW updates for your device. 
● Check your device in “Safe mode”. 
● Perform a Factory data reset of the device. Before performing the factory data reset, remember to make backup copies of all important data stored in the device.