Hi @Desmel, sorry to hear about this.
I am afraid that there is no setting available in the phone capable of adjusting the sensitivity of the touchscreen. Do you have any kind of screen protector mounted on the phone which may interfere with the touchscreen? Also, have you been able to carry out a quick test of the touchscreen to see if the hardware works as intended? Find and tap Settings > Support > Xperia Tests > Touchscreen
Another thing that you can try is to reboot your phone in safe mode to see if the touch response works better there? Safe mode is a troubleshootin mode where all apps downloaded from Play Store is temporarily deactivated, in this mode you can see whether the lacking response is caused by a downloaded app or not. for more information on safe mode and how to use it, click here.
Try this and let me know how it goes!
