Worth studying queen's gambit accepted as whitw/black?

Is it worth studying how to play the queen's gambit accepted as either white or black?
What do you suggest to play against queen's gambit as black?
And why does my trainer not like 1.de-d5 2.c4-Kd7?

I never liked this opening, no matter if playing white or black.

QGD, Queen's Gambit Declined, you get a comfortable position with Black. But for White, I don't even think of playing d4.

Someone will one day accept the gambit. It’s best to know how to play the continuation

@WassimBerbar said in #3:
> QGD, Queen's Gambit Declined, you get a comfortable position with Black. But for White, I don't even think of playing d4.
Then prove same by defeating Carlsen who is playing QG against you!

@bayonetCHARGE
Best opening for White is Queens Gambit and best opening for Black is Sicilian defense. (According to statistics)
They are more than worth studying and complex enough to get puzzled.
I don't now about Kd7 idea as I respond to 1. d4 with my most successful, Benoni c5.
Rest is upto you.
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