Start in Beijing, end in Hongkong?

Hi, will it be a problem if I am entering China in Beijing with a German passport (15-day visafree), travel around and go from Guilin to Hongkong via Train to fly back home from Hongkong?
Since HKG is considered a foreign country in terms of visa regulations, I know that often at passport control the officer ask for the return flight. Will it be a problem when this flight is not in Beijing or other chinese city but HKG?
Do the 15 days visafree include HKG? Meaning, can I travel two weeks in china and then additional days in HKG?
Thank you very much in advance.