Restart my iPhone 6s

You can try resetting your phone with itunes to remove the password, this will cause an activation lock however if you have fmi on, so check that before doing the itunes reset. You can check it through putting your imei or sn (should be on the back of your phone on small text near the bottom) and putting it in this website https://imeicheck.com/icloud-check. If fmi is on, you need the icloud email and password of the account already signed in, and if you do not have those do not reset.