You purchased possibly the least efficient headphones that you could! Excellent rep' that Beyers have for sound quality they have a lowish sensitivity of 94dBSPL (for I assume 1mW in?) most phones are at around 100dB, This 6dB loss would hardly matter but that it is compounded by a much higher impedance than most modern "cans" of 400Ohms. 32Ohms is a common impedance these days with 100Ohms being about the upper limit.
He said he was a novice. Why all the tech guffaw without any explanation of your points (correct as they are)?
I'm All Ears.