Why is there some games what I can't give out here?

Did you pay 10 Euro for it?

Well, because only one source gave it out for free (dlh.net). Everywhere else you have to pay money. It would be the same if you missed a promotion where a game has been given away for free. Once given for free - not giveawayable anymore for all eternity to avoid exploitation of Contributor Value (CV).

Forget about the official price at Steam store. If it has been given away for free before, the game is banned forever to avoid exploitation of CV. You can see the complete list of banned games here:

http://www.steamgifts.com/bundle-games

Because Steam has no shame.
A lot of games on Steam that are 10 euros and less in the Steam store have been given away in bulks of tens of thousands at various official and unofficial sites, both in the past and most likely in the future as well. Which means they are essentially worthless since you can easily find traders that'll fork them over for a few cents in profit (didn't cost them anything to stockpile). If you buy them off Steam, Steam is ripping you off for the full price straight.
Same goes for many bundle games which are mostly near-worthless but still costs marginal amounts of money to obtain, but way less than Steam store prices.
Moral of the story: Never buy anything on Steam, and if you really really need to, do some serious price comparisons on other sites first.

that would help a bit, yes.