This was off-topic in Writing so now it's in Business/Law. First thing is you need a good Collaboration Agreement. Here are some examples of what can go wrong if you don't put anything in writing. And of course, don't recruit in this thread - use the Hobby Project Classifieds for volunteer/unpaid recruiting.  

Hi Jan!

I like History and i Like Strategy games, your idea sounds like it could be interesting. It sounds like you have put a lot of effort on preparing your idea. In what part of history is your game going to take place? 

I might have some useful hints for you. I have no idea how detailed your plans are and how you have structured the information. You should read up on how software and game development teams describes the work that needs to be done. This will help you to structure your information in a way that is natural and easy for a development team to digest. You should try to find someone with experience of managing open source projects.  The best would be to bring this someone on board the project, but at least gather information about how to do it and what pitfalls to avoid. One important thing you will have to consider is how you will licence this open source software? https://choosealicense.com/ Picking the right licence can be crucial to move the development in the right direction and protect the software from misuse.

To manage an open source project takes a lot of efforts.  I think many open source projects tend to consist of people that put in a lot of effort to create something that is useful for themselves and others. Then others that find it useful can contribute with parts that is missing and might be valuable to them.  So you will probably have to find at least a few good devoted developers that can help you to get up to speed and create an interesting foundation that can attract more contributors. Managing a Game development project also takes a lot of effort and skills.  

As i see it you at least need to acquire knowledge in some areas either by learning it yourself and/or by cooperating with someone that does know.

• Managing an Open Source project
• Managing a Game Development project 

You also have to figure out how to attract people with different skill sets to the project. Why would they chose to spend their time on your idea? Why would they want to work for free instead of making their own thing or working for pay? You have to promote your idea and convince people to put a lot of effort into this and they will expect some award or find the work very awarding to join you. 

I wish you good luck!