Steam Trading Card problem

No, you only get a certain number of cards. The rest you get through trading or steam market, hence trading cards.
Valve implemented this feature so they could get more money via market while ignoring the features the community wants.

You misunderstood. You get 50% of total number for each game by drops. The rest, if you want to craft the badge, you have to trade/purchase.

You get 4 key for playing, the other 4 through trading / buying them on the community market.

YOu can have a look at your badge pae for more info.

you missunderstood that you can earned allways only the half cards so on left4dead thats are 4 the other 4 you can only trade or buy on the community market for every game gives 5 lvl and one foil lvl. so you need to complet the badge on l4d2 40 Cards. Thats the point while the cards are rare.

Ok, thanks for the clarification.

There are Left 4 Dead 2 cards and nobody told me?

but when you say i dont wont this cards i take them actually for a civilization 3 game :)

I had this exact same misunderstanding. Basically look at this. So in short, you are only able to find half a set for every game with TCG you own. The rest have to be obtain via trading with other users or buying them on the community market.