I don't know how it's in Germany but I'd imagine it to be pretty much the same as in the Netherlands: most if not all contracts will have a trial period where the contract can be terminated by both parties on the second.
This is the risk of changing a job, even more so if the new job is in another country.
edit: based on some other comments in this thread the German law on this does not seem to be the same as the Dutch laws.
When you give your phone number to LinkedIn you're not surprised either if people will find your job title, photo and name based on your phone number right?
I'd think most people are pretty aware of how public the Whatsapp info is.
> Perhaps somewhere out there, in one of those galaxies I spent my life researching, there already is a known unified theory of physics, with a variation of MOND built into it. But then I think: So what? We still had fun doing the math.
This is the risk of changing a job, even more so if the new job is in another country.
edit: based on some other comments in this thread the German law on this does not seem to be the same as the Dutch laws.