How to set navigation/GPS sound settings and FM

For setting  navigation/GPS sound settings and FM synchronized sound, louder sound effect

(1)can you double check the"FM "icon in main screen , 
open it, and see if it has ticked for using?
if yes, pls untick it,and confirm the option at right top corner  
see if it can help you
(2)when you turn on the FM transmitter ,you can not hear the voice from GPS , please check below setting:
please press the "setting " icon on the main menu ,and then press "volume " then you can set the volume of the device .then back--FM Transmitter, check whether you have tick "Use FM", don't tick it, save and back.
(3)set the voice on the navigation program:
Car GPS :
press "navigation "--"more"---"settings" ---"sounds and warning " --"volume" , and then please set all the option to the max volume .

Please have a try , if not work we will give you other solution.
Regards