Hi,
You need to remove the back cover and then remove the first covering of the phone.
After that you can try removing the speaker located at bottom right.
Speakers are rectangle shaped and black in color.
Clean them and check if contact pins are misplaced.
after that place them correctly and attach the covering.
Check if it works.
Please note that you dont need to dissemble your phone, just open the second covering with screw driver and you can see the speakers or use any iron and look for magnet at bottom.