I could see my screentouch was not responsive. I haven't dropped it or caused any heavy impact on it.
Eventually, I used screen test then it showed me this, what should I deal with this?
Hi @DesmondC, sorry to hear about this. 
Since it is a very specific area of the display where the touchscreen isn't working it does sound like this is related to hardware and not software.
I would however recommend that you remove any screen protector that you have on your device and see if there is any change.
If you experience the same behaviour without the screen protector, perform a software repair using Xperia Companion to rule out that this is caused by the software in your device. Do note that the software repair will delete all data stored on the internal storage so creating a backup using Xperia Companion is advised.
Do the test again after the repair is completed and if you still can't use the entire touchscreen, your device will need to be examined at an authorized service centre and your Local support will assist you further.
Let me know if that helps!
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