I don't have anything new to add Yiorgos T -- if it's not 2-step verification or a typo I'd recommend resetting next. Resetting your phone returns it to the state it was in when you took it out of the box, removing any personal information you had on it like photos and settings. Depending on which version of Android you're running, some settings can be backed up from the cloud (In Android 4.0 you can find that setting under Settings > Backup & reset, under older versions it's usually found under Settings > Privacy).