How to Fix a Slow or Unresponsive Samsung Galaxy Touchscreen
To fix a slow or unresponsive Samsung Galaxy touchscreen, first restart your device. Remove any screen protectors or cases, and clean the screen with a microfiber cloth.
Update the software in Settings , Software update. Test the touchscreen using the diagnostic menu by dialing *#0*#.
Boot the device into Safe Mode to check for problematic third-party apps, and if necessary, perform a factory reset after backing up your data. If issues persist, visit an authorized Samsung service center.