You’ll wake up with Carmina’s help. This mission will serve as a tutorial to learn some fundamentals of the game. Follow her along the river. Check out the dilapidated sheds and buildings along the way to find loot inside. Continue until you reach the old mine building. Scour the building for materials. When ready, use the workbench to craft a Saw Launcher.
Leave the mine building and follow the dirt road leading to the bridge. Take out the two highwaymen along the way. Once you reach the bridge, it’s up to you how to deal with the enemies. There’s an MG emplacement facing the main entrance so I suggest attacking from the side. Don’t forget that you can already craft throwables like the molotov and baits. Use these to your advantage.
Once the area is cleared, head to the tunnel and enter the door. After the cutscene, mission is complete.