I have looked at my ICE DB ticket and the train number and time is different to the one available on the website for seat reservations. Is this because they didn’t run that train? The destination is still the same (Köln to Berlin) just a different arrival time. Now I am scared I reserved the wrong seat on the wrong train. I did book the Flexipreis Europa. Can someone also explain what it means?
A "flex preis" ticket is a flexible ticket, valid on any train that runs the route you bought the ticket for. So you can take any Köln to Berlin service on the days your ticket is valid (see the top of the ticket).
Your reservation will be for a specific train, but you are not limited to taking that train. Just when you take another train you will not have a guaranteed seat. Your reservation should have the train number, the car number and the seat number on it.
Given that you have a flexible ticket you do not run the risk of being on the wrong train, as long as you are on the right train route.