Forget pattern

The only solution is to wipe your data via recovery mode. 

Connect your device to the laptop or PC and long press the volume down button + the power button, the device will turn off after 10 seconds, then press the volume up button + the power button to see the Samsung Galaxy bootup screen, release the buttons 

You will enter the recovery mode 

Go down using the volume down button to the option 

Wipe data / factory reset 

Press the power button once to confirm resetting your phone  

Then choose 

Reboot system now 

To restart your device