If you refer to 1. d4 d5 2. c4 e6 3. Nf3 or Nc3 followed by Nf6, then you are facing the Queen's Gambit Declined, also known as the Orthodox defense. It leads to very solid and positional play by both sides. The Orthodox defense is very flexible and could in theory be played against many other openings that do not involve white getting an early pawn on e4, including the Colle, the London, the English, the King's Indian Attack, and the Stonewall. Its biggest drawback is that it blocks in the light-squared bishop, which may be difficult for black to get out.
The Q.G.D. is a very solid and positional opening and to play against it, I just recommend developing your pieces normally. If you play the Queen's Gambit and are thrown off by this response, then maybe you should study some theory because this is one of the most common methods of declining the Queen's Gambit.
What is d5,e6,nf6? How do I proceed, I always fall into trouble with this