Telc B1 mundlich Teil - Typical Themas

I think you are wasting your time asking such a question because it could be anything. You cannot really study for this, it is designed to be a chance for the evaluators to get you talking and see how you handle a conversation. Makes no sense to study any particular subject. I did this test about  6 months ago. They took 2 people at a time and asked them direct questions and had them converse with each other.

Search online for "Telc b1 test" and you will find plenty of practice tests with example topics. To get an idea of what types of topics might come up, look at German books for levels A1, A2 and B1 and what topics are covered in each chapter: Travel, family, movies/series, hobbies & freetime, the world of work, etc.

Topics they won't expect you to dicuss: history, politics, current events, religion...

Section 3 for speaking is "zusammen etwas plannen." Could be a Grillparty, a birthday, an outing, or anything like that where you have to discuss and settle on date & time, location, what to bring along, and so on.

As Tom said, you can't really _study_ for this (except for increasing your vocabulary about the various topics), but you surely can practice. Pick a topic - travel - and talk about it. Where have you traveled to recently and what did you experience there? What are the pros and cons of traveling with an organized group vs. alone or with a friend? Where do you want to travel to next and why? What problems have you faced while traveling and how did that turn out? It's best to practice with someone whose German is better than yours.

Have fun and good luck!