I have a booking with 2 separate travels days:
1) Lausanne-Bern-Basel-Berlin
2) Berlin-Basel-Bern-Lausanne
I’ve done this journey a few times before. I always took a 1st class “Super Sparpreis Europa” with seat reservation for the Deutsche Bahn train, which is the Basel<->Berlin leg. For this booking, I have a seat reserved for Basel-Berlin but I was unable to book a seat for the return section. I know this ICE train has booked seats. What will happen, how do I get an assigned seat?
See differences below.

