How do I fix my iPhone microphone?

If she hears you it it not your microphone that is not working but your speaker.

Please try this

1. Remove all screen protectors, films or cases from your device. 
2. Check the opening of the speaker to see if it's blocked or dirty. On iPhone only, make sure the receiver isn't blocked or dirty. 
3. If necessary, clean the speaker or receiver opening with a small, soft-bristled brush. Make sure the brush is clean and dry.
4. Go to Settings > Sounds (or Settings > Sounds & Haptics) and drag the Ringer and Alerts slider back and forth a few times. If you can't hear any sound, or if your speaker button on the Ringer and Alerts slider is dimmed, your speaker may need to be serviced.
5. If you can hear sound, try making a call with your iPhone and turn on speakerphone. On iPad or iPod touch, make a FaceTime call. If you still can't hear anything, or you hear static or crackling, then your network or reception could be the issue. Try calling again later or from a different location.

If this is not working  contact Apple Support to discuss service options.

zosia192 Said:

" want talk with my mom but my microphone dosent working. For example, she hears me"

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Troubleshooting iPhone Mic:

Your post's work contradict. Whichever is the case, read he following...

Did you Install any Updates?

If so...

A. Go Here: If you Hear No Sound or Distorted Sound from your iPhone, iPad, or iPod touch Speaker - Apple Support

B. Volume Input: if your Microphone isn’t Working or People Can’t Hear you While you’re on a Call -Apple Support

C. Restart your iPhone:

Having just installed an update, restart your iPhone (as you always should after any update install): Restart your iPhone - Apple Support

You need to give us more information. If she hears you on a phone call, your microphone is working.