Hi @Omjana, sorry to hear about that. 
Could you please elaborate a bit on what you are experiencing with the touch screen, is it tapping on things by itself or is it slow? The more information you provide us with the easier it is for us to help you!
If you have a screen protector on your phone, I'd recommend that you try and remove this and see if that changes how the touch screen works. You can also try the touch test in the inbuilt test in the phone which you can find in Settings > About phone > Diagnostics > Test > Touchscreen.
Let me know how it goes!
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