I prefer this forum.
Why is that?
would you care to answer my questions?
As I understand it, your father left a will but didn't make provision for you in that will, therefore you're invoking zachowek (if he died without leaving a will you and your step-sibling would share the estate between you equally).Under zachowek, yes, you would get one quarter of his estate.
You mention real estate - you say your father had a 50% stake in it. That complicates matters a bit as his stake becomes part of his estate and you and your step sibling will each own a quarter share of the real estate but to get the cash value of it would require the cooperation of the surviving owner which is not a given.
As to how the money is transferred bank transfers are the usual method of payment these days in business transactions in Poland.