@yehualashe68096 let's assume that your proximity sensor is not (yet) broke, Check the make sure that your screen protector is not blocking it (or a case if you have one one there. Make sure that the top left edge of the phone is not covered. That is where the proximity sensor is located.
Since this is an Android phone, there should also be settings that may have disabled your sensor. Go to your settings and check for something like "Call Settings" or similar and see if the sensor has been disabled.
After that, if nothing works, time to return it!