I am a software engineer in Germany, I had an issue and i don't know how to react:
Several weeks ago i had a job interview with a recently founded startup; I met with a co-founder of startup and we had an interview more than an hour long. The first of the things he talked about was that they had just founded the company and needed someone who would commit to the company as a technical leader. The company is going to have a mobile app aimed at a specific sector; but the guy didn't know anything about software world. I explained my experiences and I told how should they behave, which kind of technology they should use, what is the profitable approach to develop this application.
The guy really liked what I said and offered me a job. We had a deal but without any contract; because he offered me a salary that did not make sense for me. After i denied this salary he said the salary is negotiable, he can rise my salary and share a part of revenue with me; but he also asked about time to clarify this topics.
We had two more time meetings and several phone calls and a lot of mails and text during this time. I shared with him some more information about technical issues. I did some research and I shared the results with him. Everything was ok and I was waiting for the contract, but yesterday I asked about the salary that he is going to pay and some more topics about work via a message and today he just call me back and said he can not work with me without giving any more details.
Now I want to ask, is this legal? Can he use information that I shared with him like profitable technology choices?
I don't know someone else who has had similar experiences; but it really bothers me and I just want to hear some expert's ideas.