On Android phones you can activate a feature called pattern lock. This feature can be compared to a Windows computer asking for password after the screen saver kicked in, only instead of a password you use a pattern. You get a screen with 9 dots and you draw a pattern of your choice with 4 of them. If you forget your pattern (or have kids that likes to play with phones) you will after 3 faulty attempts be unable to use the pattern to unlock it. Instead you are asked for your Google account and password (that is setup with the phone of course). This is where the problem starts.
Warning! All data will be lost!
1.Press together volume down + power button
2.Keep press untill recovery menu appears
3.Choose with volume buutons “factory reset” and select it with power button
4.Wait until the phone restarts