My phone switched off and it doesn't work why?

@abdisa the white lines could have been an issue with your screen. Does your phone give you any sign of life? Any vibration when you turn it on? If so, it is your screen that has failed. If it doesn't do anything it is possible that this is a main board issue. It is also possible that this is a firmware issue. Start off by trying to attempt a forced restart.

Press and hold the Power key for 30 seconds.

If the phone starts to power on, release the Power key.

After that try a soft reset:

Hold down the volume and the power button for approximately 10 seconds. This will reboot your device.

Should that not work, follow the Samsung Flowsheet

Next use this document Component Layout and with the search function of your PDF reader, find the components listed in the flowchart. You can then take the voltage measurements as directed in the flowsheet.