DB reservations can't be cancelled. You'll have to book again if you want a reservation for another train.

You can also book seats on DB trains via CD at cd.cz/en for CZK 75 (~€3) per person and train. You can cancel those reservations until 15 minutes before departure and receive a full refund.

Thanks! I did not know about the CD route, great tip!

Is there a way to grab a specific seat using CD? I wanted to book one of the single / solo seats, but if I look for available ones on DB and enter as “specific seat” on CD I just get an error. It only seems to work with auto seat. Any advice?

I'd expect it to work with the coach/seat numbers from DB (if the seat is free) but I must admit I've never tried it.

Via CD you can ask for a specific seat. You have to provide coach number and seat number. The seating plan you can look on the website of DB. But I never tried to book.

5,90 means 1st cl (2nd is 4,50) and these have rows of 1 and 2-I assume (but not sure) that single pax will first be put by system in the single seats-when I had a 1st cl pass and used DB extensively it was clear that most business pax on weekdays were single and the aisle seats in the 2-rows were always the very last to get taken. Normal tickets for 1st come with a free RES in Germany. Most seats are only marked as ´can be RES´ so this is not very useful to see where you can site for long trips