Hi @Honda69, I am sorry to hear about this
Your post has been translated to English as this is an International forum, Please post any replies in English and it will be easier for me and other users to assist you.
Could you please elaborate your question a bit? Is it the main microphone or the secondary microphone? Is it during calls that you are experiencing this or during other usage of the microphon such as recording videos etc.?
the XZ-model has a total of two microphones. A main microphone located at the bottom of the display used in calls and a secondary microphone used for other recordings such as video and calls on loudspeaker. To see where these microphones are located, please see item 6 and item 12 the overview of XZ.
Do you have any kind of protective case or a screen protector mounted on the phone? If so, you can try removing the case or the screen protector in orde to see if the sound quality improves. another thing that you can check is so that there is no water or dust blocking the microphone or the area around the microphone.
I would also suggest that you use the Tests feature in the Support app to carry out a quick test to check that the loudspeaker is working properly. In order to do this, fins and tap Settings > Support > Xperia tests > Media.
Another thing that you can try is to reboot your phone in Safe mode. All apps downloaded from Play store is deactivated in safe mode and by doing this you can see if there is a downloaded app that is causing this. For more information and instructions on how to enter safe mode, please click here.
If none of these measures work to improve the sound from the microphone I would suggest that you try to perform a software repair using a computer and Xperia Companion. Please note though that a software repair will erase all user data, so remember to do a backup of your user data first.
Try these measures and let me know how it goes! 
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