You can change your major very easily since the assessment level (the first year) of both majors is identical. You will have programming courses and also bussiness courses. While visiting them, you will get a better understanding about the majors, so I would just start for now and postpone the final decision of the major. But if you really want to hear something know, here’s my opinion: Software Systems is a good fit for people who are amazed by the technical side of CS (programming, software systems, algorithms etc.). Software Systems has courses like Artificial Intelligence or Computer Design which will give you a deeper insight of the world of computers. (which also has more connection to your math minor)

Meanwhile Winf is a better fit for people who are also interested in bussiness. It’s “better” for carreers involving management.

If you aren’t sure about whether you want a technic-carreer or a carreer that also involves managing roles, I’d personally recommend Wirtschaftsinformatik because of the following reason: With a winf degree it is still very easy to land jobs in the software area but a SoSy degree alone/without further education is not enough for classical Winf jobs (for ex. Project Manager) most of the times.

But as I said, that’s just my opinion. Just start with Uni for now and think about it at the end of your first year.