Welcome to the Wefugees Community and thank you for sharing your question.
Our platform and our experts are based in Germany, therefore it might be difficult to give tailored answers regarding Austrian immigration and residence law. However, I assume that it will be very difficult to get a Austrian visa for Syrian nationals to marry in Austria. If you want to marry in Turkey, you will need to apply for a Turkish visa respectively. In Germany, for instance, married couples need to fulfill certain requirements (like being independent from social money) for a family reunification visa.
I will link two of our experts here as well. Dear @mbeon-caritas or @mbe-on_Zsigó, can you give any advice or add information?
All the best,