When I was looking around the camp site, i found out u can hop on a fence walk to the bridge. Get on the wooden pillar below. And roll onto the other wooden logs on the other side. From this side I could open up the bridge. After exploring a little bit more I found an Obsidian Chest on the top of the mountain in the back, and also found a nether portal. So i don't know if I was supposed to go here?  So I did more exploring. Restarted the world and the bridge closed again and can't open it again.