besides a forum, what can i do in order to have a site where people ask questions and people answer them, more of like an automatic thing not searching through forums and stuff?
As long as you keep your forum pruned up and the spam amount low and have it structured in a way that makes sense, they are pretty easy to navigate. Or as smallfish said, you can use a blog, but from what I gathered in your post, your looking for a community type thing. In which case a forum would be the best bet. As for the forum systems: I would recommend IPB over any other, it's very user friendly and has an admin panel that makes sense (something VBulletin and PHP-BB lack) Hope this helps.
When we mention Q&As the first thing that comes to my mind is "Social networks" The blog is a really nice idea, but it would be really difficult for you to generate traffic and urge the people to comment and discuss topics. I'd say that it would be way easy for you to just have a website where the people will post the topics/findings or whatever you want them to talk about (you could have like categories or something predefined). This will increase the user generated content and it will most likely boost people's participation.
Do you mean something like Yahoo Answers? I'm not sure, you could probabaly take a blog script..and make it into something similar to this by allowing all users to post questions, and using the comments system as answers. Then you would just have to organise it all to change it from a blog layout to your needs, which wouldn't be too hard. Maybe there is already a script that does this for you. So you need to go searching for some scripts unless you know PHP etc. already. You should spend as long as possible to make the layout and script to your needs, as once it is finished your site would be pretty much automatic and you can watch it roll!