Switching from industry to research(informatics) Backstory: I was working in a research institute as a research assistant during my bachelor and master phase. I received my M.Sc.(informatics) about 2 years ago and since then I am working for a company in the industry as a software engineer.

A few weeks ago, the professor I was working for in the past gave me a job offer at his institute. Basically he wrote out of nowhere and I was very glad and accepted his offer. A condition for me to accept was that I can pursue a Ph.D, he said yes.

Now I face a very troubling problem: I have never written a paper in my life. 

I wrote some things during college but nothing that was actually published. I like reading papers, but reading and writing is a different story...I was also not really involved in actual research, my previous work was concentrated on programming. Now I am a bit worried that I might make a bad appearance in my first weeks or months, I guess the professor thinks highly of me(for a reason I don't know) since he gave me that offer. 

I have 3 months until my new life as a full researcher, with a complex research field I almost know nothing about. I am worried that I sit in meetings and do not even understand the basic concepts of their research. 

What can I do to prepare myself for this situation/job?
First, don´t panic.

Second, when you start as a researcher, most professors will accept that you are far away from perfect - however they expect your hard work, your willingness to go through an intensive thinking process and so on. Typically, you will be in a more or less intensive coaching environment, where he coaches you. Of course, the majority of work has to be done by you. 

The theoretical part will grow. At the beginning, you will have intensive research of what others are doing/have done. You will read many conference papers and on that way you will learn much about your field as well as academical argumentation. If you want to start now, go to an academic library, search for Journals and conferences on your topic and start reading.

My PhD took 4.5 years, and it was not always easy, however, it was worth doing it.