Got a question here. Obviously we all know the faceless Men can change their faces and any one of them can be anyone and I assume j aqen was not always the same person Everytime we see him. But how do the other faceless have the knowledge of what the other ones wearing his face had concerning Arya? Also in the scene where he takes the potion to kill himself to save Arya after she kills meran tyrant he is still wearing the face while lying dead on the ground but then the Wait who is standing behind Arya changes into his face as well so we now see to jaqens at the same time?

How do they share info about Arya and hold the same plan and feeling towards her? How are there multiple jaqen faces??