ACL is an intermediate topic (at least) and if someone needs to create a more complicated ACL configuration, needs to have a solid base of relevant knowledge and past experience. Experience can be gained by working with simpler ACL setups at first, and going to more advanced and complex setups as long as someone understand how things work.
It's not easy to swim directly in the "deep blue sea" of the ACL, if there is not a clear understanding of how it works.
Simply because the end result not only won't be the expected, but the project might end up in a total mess and a not functioning website at all.
You said you don't fully understand Joomla ACL - This immediately means that you need to read more and experiment more with it. Do not try immediately to accomplish your complex requirements, because most probably it will create frustration to you. Start with a very simple project.
If you are in a rush and you need to accomplish a such task for your business, then better hire a professional to do this for you.
That's my advise...
More reading / Tutorials about Joomla ACL: