A college of my girlfriend has forgotten the unlock code of het Samsung phone, I wonder are there ways to break/reset it, with or without loss of the stored data ? Or are only professionals able to bypass this lock with external software or something like that ?

See image.

Take it to any Samsung shop. I'm talking about the actual Samsung shops and not general phone shops. They can reset the phone but unsure if they can save the data.

I recently had my Note 1 unlocked which included an upgrade to Note 2 software which took about 10 minutes for 280 Baht.