Which is the best defence against 1.d4?

It is pointless to suggest the Nimzo Indian because White in our days tends to avoid 3.Nc3 almost 80%. At least that is being showed on databases.
Since you are already familiar with the Carlsbad structure, I think you don't need to change much this and go to Indian defenses and structures.
My suggestion is to study the Ragozin in case after 3.Nf3 White plays 4.Nc3 and the solid Semi-Slav when White transposes to a Catalan territory after 4.g3.

Nimzo Indian and Queen's Indian needs a lot of study and the ability to handle many different positions.
It will be better to choose Queen's Gambit.
Accepted doesn't need much theory.You need to study well the dangerous 3.e4.The other lines more or less have common sense moves.You need to know how to play against the isolated pawn but if you don't you can avoid it.
Declined also has some interesting defenses.Tartakower is very good if you can handle the "hanging pawns" positions and there is also Cambridge Springs that worths trying.
Cambridge springs is good for lower levels as it violates 1 principle of the opening-Early sortie of the queen the the opening.
But Orthodox is better than Cabridge springs I think

In some variacions i play Cabridge Springs but sometimes i can't.
Then go for Orthodox defense. It's a safe line for black.

I am playing slav and always after the opening i get bad positions.Is there anything else good against 1.d4? I am thinking about Nimzo-Indian or Stonewall with black.What do you think???
If you play the Stonewall, you better be ready for the Classical as well!
Many make the mistake of thinking the Stonewall is an all-encompassing defense.
Many violate the rules of the Stonewall. For example, NEVER let White play Bf4 and Bxd6 if Black is going to have to take back with the Queen. If the pawn is still on c7, and you can take with the pawn, that's ok.
Personally, I prefer the Old Indian, but I used to play the Stonewall/Classical Dutch all the time!

Basicly the problem is in Orthodox Defence.White have more space and better pieces.Also after Nc3 and Qc2,e4 is coming.I don't like my position at all!
NimzoBean: you're right, I play the Kings Indian Defence but the Nimzo Iindian Defence is better. The problem with the NID is that it's so good that White always doges with 3.Nc3. What to play then? Queens Gambit Declined, Queens Indian Defence, Bogo Indian Defence, Modern Benoni? I think neither of them are better than the KID. What do you play?
Pulpofeira: I'd play the Semi-Slav but I don't know what to play vs 5.Bg5? Botvinnik, Anti-Moscow Gambit? What do you play?

Pulpofeira: I'd play the Semi-Slav but I don't know what to play vs 5.Bg5? Botvinnik, Anti-Moscow Gambit? What do you play?
Problem is, too much theory for me for the moment. I'm playing QGD Lasker variation now.
I am playing slav and always after the opening i get bad positions
.Is there anything else good against 1.d4? I am thinking about Nimzo-Indian or Stonewall with black.What do you think???