Cologne to Antwerp Train

11 minutes is usually enough.

That's enough time albeit a little stress; the 1st leg Koln To Brussels is the most important

If you miss it, there is another 23 minutes later. I believe the Belgian leg is not bound to any specific train.

There are many trains from Brussels to Antwerp. Once I was waiting in Brussels train station for a train to Antwerp for a long time. There were many trains going to Anvers. Unfortunately I did not know that's a French word for Antwerp so I let them leave without me until finally the train with a sign for Antwerp came. They speak Flemish and English in Antwerp. In Brussels they speak French and few people also English.

The info you have is the quickest connection between Cologne and Antwerp(en) if you change at Brussel-Noord / Bruxelles-Nord. There are so many local (IC) trains from there to Antwerp you can easily catch the next one if you miss the one you mention without loosing too much time. The ticket for the leg between Brussels and Antwerp is valuable for the hole day it is issued. To be clear that’s not the case for the journey between Cologne and Brussels as the seat will be reserved for the specific time it is booked. But if you understand the usual layout of a railway station (and your luggage easy to handle) the 11 minutes is usually enough to change trains.

If you don’t mind changing at Brussel-Noord you can even travel the few minutes further to Brussel-Centraal / Bruxelles-Central, store your luggage in a locker there for a visit to the Grand Place and continue later the journey to Antwerp using the same ticket, so no need to buy an extra one as long as you do this the same day.

This can be a very cheap trip if you buy far enough in advance. You always have to change for Antwerp at one of the three downtown Brussels stations. As noted, there's a lot to do near Bruxelles Central. All tickets to or from Brussels are valid to/at all three of the stations. (Some trains, like Eurostar, stop only at a single station. But all trains to Antwerp that stop at one of the Brussels stations stop at all three.)

Note that Antwerp has two stations, but virtually all tourists get of at the landmark main station, Centraal. Look your hotel up on Google Maps to be sure.