The company is located around Frankfurt, its been almost two days since I replied and I didn't hear from them.
That is usually a very short time in a job hunt. Sometimes companies take multiple weeks between contact.
Also, don't wait for them to call you back, statistically they won't. But if they do contact you, don't be surprised if it is two weeks, three weeks, even six weeks out.
Companies go at their own speed. Often there is a multi-week window of getting information from potential candidates then handing it all over from HR to the people on the team. They wait for a while, prune the list down to the five or so the are interested in interviewing. Then HR conctacts all those people, and interviews take place scattered over anything from a single day to multiple weeks. Then anywhere from the same day to few weeks later they make their decision and start the serious negotiation.
If you are doing a traditional resume-based job search (protip: don't do that) The vast majority of the time you contact many companies, only a small number call you back. You talk to the HR people and never hear from most again. Then you talk to the dev teams, and probably never hear back or maybe get a generic email.
If that's the process you're using, go read the book "What Color Is Your Parachute". It has been updated every year for decades, so you can usually find one from the last few years at your local libraries or used book stores.
What do you call a resume-based job search? I guess that what I'm doing.
What are your suggestions? I'm trying to find the book you mentioned...