How to unlock the homepage-preference on Safari?

Hi everyone,

Recently my browser got "hijacked" and the homepage was permanently changed to some search engine from Hong Kong. I somehow managed to find a code that i put in 'Terminal' and changed i to Google (Homepage of safari is locked and unable to change it <-- here I found the code).

My problem is that my homepage-preference is still locked (see screenshot) and I am wondering if there's any way to unlock it somehow.

I've attached a screenshot of the preferences on Safari (it's in Danish).

Thanks!