1. do you use it mainly to make money?
Yes, but it's not just about the money, it's about changing the world for the better. Though, to be fair, there aren't many honest ways of making a shitload of money without changing the world. Capitalism's all about incentives.
2. how do you make money out of it? mining or buy&sell the coins?
Buy low, sell high.
3. how often are the big jumps in value? like 50$ differences.
Like, $50 in a day? Pretty rare. $50 in a month? Not so rare.
4. is there any official value? or do i need to go by what sits like bitstamp says? (131$)
Is there any official value of a gallon of milk? Or anything else for that matter? No, value is just whatever price a buyer and seller can agree on. If a buyer offers too low a price, nobody will sell to him. If a seller charges too high a price, nobody will buy from him. They have to reach an agreement in order to make a trade. The price you see listed on exchanges is simply an indication of what that exchange's users are currently willing to trade bitcoins for.
5. how much money do you usually make from buying and selling? im planing on starting with a small amount. like 3 bitcoins.
On average, about 1300% pa.
Note that past performance does not guarantee future results. Only invest what you can afford to lose.6. how risky is it? its not like the value drops allot for a long time so there isnt really a risk, especially if im going to mess with 3 coins... (?)
It did after June 2011. The price went from from $32 to $2 and took nearly two years to recover. There have also been other crashes since then, though none so massive, and of course the market is a lot larger now, but it's still rather small is the grand scheme of things, so don't assume it won't crash massively in the future.
Then there's also the risk of your bitcoins being lost or stolen, so make sure you encrypt and backup your wallet (in that order) and keep it secure.