do a factory reset.
Samsung S7 Factory reset:
Step 1: Press and hold the Power button until the phone switches off completely.
Step 2: Now press and hold the Volume Up and the Home buttons. While holding these two buttons, press and hold the Powerbutton until the Recovery screen appears. Release all buttons.
Step 4: Using the Volume Down button to scroll through the options on the screen, highlight the " Wipe data/factory reset" option and then use the Power button to select it.
Step 5: Select " Yes" to confirm the process. The reset will take several seconds.
Step 6: Select "Reboot System Now" and once the device reboots, set it up again and restore your data from the backup you created.