Is it possible to get another PhD in political science in Germany after getting a PhD in philosophy in Hong Kong I am doing a PhD with concentration on continental philosophy in Hong Kong (my MPhil also had the same concentration too), but I am really interested in political theory and political science and often audit relevant courses. I am wondering whether it is possible to get another PhD of political science in Germany, if I focus on empirical political science research or political theory, after finishing my current one, provided my German is fluent enough.
You should have a look at the "Promotionsordnung" (~Regulations for PhD courses) of the specific universities. As far as I know, it might not be possible to get the same PhD degree twice. They have to be from different fields. It should be possible to get two different PhDs as I know some people who achieved this in Germany.