sandroko:
So here's all of my code, now it's your turn to post all of your answer:
You need a counter to count how may digits of the code have been entered.
You need an array to store each of the digits as they are pressed.
Keep using the LCD for the User Interface, but also add some print statements into your code so that you can 'see' what it is doing.
Also think about what states your safe might be in e.g. code set/not set, opened/closed, locked/unlocked