Piece of mesh wont move in pose mode. Please help!

Hello, i have a problem with moving mash in pose mode. When i move with bone in arm it works, but rest of hand and fingers wont move with mesh. Please help me. Here is a picture.

Seems you haven’t parented the finger bones to the hand.
So when you FK rotate the upper arm bone, they don’t come along…

Parent them in Edit mode (Ctrl P)