I hear my voice echo when I speak into the phone.

Network problem

try reset the phone.

I can not hear the other person very well

seems your mobile mouth piece has some problem or not working. you can get it fixed from a local mobile shop..its cheep..... It will be lick this thanks for rating Good luck

just down the mic volume and see als run the sound diagone test.

I dont know on this exact phone but here is for a similar see if this will work for you.

First make sure the User profile you activated has the Ring type set to Repeat so the ringtone works continually
rather than ringing once & stopping! Go to Main menu => Settings => User profiles => [Select a profile] => Customize => Ring type = Repeat
Save the settings & as you back out of the menus make sure the profile is Activated, as it should have a large green checkmark next to it.
If this setting is already set to the Repeat option, and your ringtone does repeat, but just doesn't seem to ring enough times, read below.

Also see if your phone has the below settings somewhere in your phone's menu system. As firmware are different so can the menu system
be different. If you cannot follow the exact path to find the option below, look in other areas of your phone's settings for the settings, but
know that your phone just may not have the same settings anywhere.
Call History => General Settings => Sim1 Call Settings => Call Divert => Divert if no Answer => Activate => To Voice Mail =>
Now choose the time length you require, 5, 10 15, 20, 25 or 30 seconds.

You will need to send you phone in for repair since the mic is part of the mainboard and will need to be fixed by tech or they will probably just send you another phone.

Well, try to record something onto your mobile and check if the recorded track echos at different instances...If yes, have your mobile speaker checked withthe vendor.. If not, clean up the vicinity of the speaker... 

Try to keep the mic at a disttance and spek if you keep the mic near or the volume high you will definatly get that problem......

just wondering
probably the one ur speaking to on the other side of the line is set on hands-free/speaker mode that's why it seems that ur hearing ur own voice or something.
try also lowering ur own phone's volume level a bit.

if problem persists, consult an tech expert on this.