Can you hear people when they call in? If so, then the sounds are working and it may be something in the settings or an app.
In this case I would check your sounds in "Settings" to make sure the volume is turned up and and not muted. After you have checked in there, check all recently installed or updated apps as well as any apps you have changed the sound levels in or turned them off in. Some apps will effect the whole device.
Now you are are just talking about not hearing things you have been trying to use a microphone for, then the problem may be the microphone. Try disconnecting it and see if the phone's internal microphone works for you.
If the problem is different than these, as I had to use a translator to read what you wrote, please reply to this thread. In English if possible.