Do someone here know how reputation system worsk?

It doesn't.
Or a longer answer: you gain +1 reputation for each day that you are active in the forum. You also gain reputation for people upvoting one of your posts and for helping. I.e. when you post something that is marked as answer in a 'Question' thread, you get +5. You lose rep if people downvote one (or more) of your posts. But since there are some trolls around who use alt-accounts and scripts to systematically downvote some other people and upvote themselves, the reputation actually doesn't mean anything. So just ignore it. It is being abused since years and GOG couldn't be bothered less about fixing it.

You get 1 reputation per day on each day you post something
You get 5 (iirc) reputation when your post is marked as answer for question/problem topics
You can gain reputation if other people upvote your post enough
You can lose reputation if other people downvote your post enough
You need certain reputation to be able to post links (7/10?)

Do note that there is basically no limit on how much rep you can gain/lose by upvotes/downvotes (there are people on forum that have -1500 or lower reputation (yes, that's negative 1500 or lower) so you can gain or (more likely) lose lot of reputation per day. This is because system is real easy to abuse just by finding as many posts by person and up/down voting every one of them.

Minus 2000,I'd like to see that.Where?

I thought you had broken the record already! Have you been slacking off! Get back to work lowering your rep!

Yes Sir! Now what's this crap about -2000?

You seem quite jealous :)

Nah,just an unbeliever.

Just because a system exists and has some output doesn't mean it works. CIP, it doesn't.