The Department of Geosciences doesn't have a limited course offer that only applies to international students. Therefore, you are free to choose (almost) any course you want from the course catalogue. There are only a few aspects to take into consideration. You need to consider the language of instruction and how advanced the course is to see if it matches your level of studies. Also, some courses include a field trip that takes place during the semester break but is still relevant to complete the whole module. Consider if staying in Berlin longer for such events would be possible for you. You might not be able to attend modules that require attendance during two semesters if you are only here for one, for example those requiring the preparation and conducting of own research projects. 

The FU offers some classes especially for international students which you are free to choose as well. You may also take languages classes.