Скачать или смотреть Secret Room in World 1 Zone 2 before the last checkpoint - Guild Wars 2 Super Adventure Box GW2 SAB

The First bouncy you can also reach by aiming for the branch to the right of it
Getting back down, just walk forward (don't have to jump or anything)
Doing the difficult jump part around the tree trunk you can try the technique shown in the video: Aim yourself 45 degrees off the trunk, hit forward and jump off, turn your camera to face the other side and hit the appropriate strafe key in conjunction with the forward key.
(Alternative Jump Technique): Get to the corner of the jump, strafe jump off while holding forward, jump across holding forwadr, strafe back onto the other side. Just a matter of practice, I haven't done it this way before and don't know how it works very well.
The room itself is a part of an achievement
The room also contains a bauble in the middle of the air which you can reach by jumping on the sides and then to the middle of the room, part of a different achievement.