If you select punctualityon the bahn.de website and enter your booking code, it will show you
- If your trains are on time
- The arrival/departure platforms
- Further connections
Please be advised that these platforms can change on short notice. But don't worry, your platform and the platforms of connecting trains are announced when arriving in a station.
Aside from that, 19 minutes is more than enough time, even if you have to ask for directions. Karlsruhe has a relatively small station.