Hi Robert, welcome to the forums.
I can't speak for anyone but myself, but I think you will get a better responses if you ask for help on little chunks.
For example, it seems right now, you need to focus on the datbase structure first. When I'm working on structure, usually I'll do it with pencil and paper first to write down all the tables and fields I need to make. Once it makes sense, then I start creating the database.
Once you create that, then proceed with creating your functions.
There are many ways to do this. I'm curious, why don't you use something that has already been made, like
phpBB?
What your asking isn't something that someone can just help you with as a whole unless they wanted to devote a lot of time there with you. Even for an advanced programmer, forums aren't the simplest thing to write.
My advice would be to take it in small bites, .. ask very specific questions here and you are sure to get answers. I am more willing and able to answer a specific question rather than how to do an entire project.