After collecting the materials, return to the first floor and head left. There's a material behind the pillar on the left.
There are enemies on the stairs that need to be defeated. After killing them, head to the right side of the stairs. You'll see a resource chest ahead. You don't need to jump over the wooden planks in front just yet.
Continue forward, defeating enemies along the way. There's an item on the pipe to the left that you can pick up.
Head right along the main path. You can also shoot down the resource bag above the stairs ahead with your bow.
Shoot it down, pick it up, and head up the stairs. Defeat the enemies on the stairs and grab the purple item next to them.
After picking it up, go up the stairs again. After walking for a bit, you'll reach the outside, where there's another group of enemies to deal with. Be careful of the self-destructing fat guy around the corner of the stairs ahead.
After it self-destructs, walk behind it to obtain Black Stone Fragment #1.
