Queen Gambit Trap

There's many of my opponent in real chess has been trapped by this famous opening.. even my senior co-worker considered the best chess player in my office & neighbourhood, most of them play chess ending very well but unfortunately didn't learn any opening theory... so sadly their chess ending skill is useless.. since their beaten at opening humiliately.. mostly they are 1. e4 player which unprepared about how to play black against 1. d4 d5 2. c4