Hi! I'm at the part of "the Corneted Rat" main quest where I'm supposed to talk to a certain old man called Esbern. Upon first encounter with him when talking through a door, he barely talks and the dialogues appear for only a fraction of a second. I've managed to convince him that I'm an ally and he tells me to open the door to talk to him but the problem is that the door won't open (at all).

I'm stuck until this problem / bug is solved =/ And I don't know how to solve it.
Please help me, I can't continue playing the main story until this problem is solved.
How do I solve it?

I saw a video someone put on YouTube that I think was about this bug. It showed them repeatedly picking some book off the table every time he dropped it, and spamming the talk button with him. He never spoke, but eventually the quest became unstuck and the door opened.